[PATCH v3 0/14] implement @{push} shorthand

[PATCH v3 0/14] implement @{push} shorthand

[Jeff King]

This is a re-roll of the series at:

  http://thread.gmane.org/gmane.comp.version-control.git/268185

The only changes here are the addition of patches 2 and 6, which are
both cleanups that help make the other patches more readable/sensible.
They are the same as what was posted during review of the thread linked
above.  So there's nothing new here, but of course fresh reviews are
welcome.

  [01/14]: remote.c: drop default_remote_name variable
  [02/14]: remote.c: refactor setup of branch->merge list
  [03/14]: remote.c: drop "remote" pointer from "struct branch"
  [04/14]: remote.c: hoist branch.*.remote lookup out of remote_get_1
  [05/14]: remote.c: provide per-branch pushremote name
  [06/14]: remote.c: hoist read_config into remote_get_1
  [07/14]: remote.c: introduce branch_get_upstream helper
  [08/14]: remote.c: report specific errors from branch_get_upstream
  [09/14]: remote.c: add branch_get_push
  [10/14]: sha1_name: refactor upstream_mark
  [11/14]: sha1_name: refactor interpret_upstream_mark
  [12/14]: sha1_name: implement @{push} shorthand
  [13/14]: for-each-ref: use skip_prefix instead of starts_with
  [14/14]: for-each-ref: accept "%(push)" format

-Peff

[PATCH v3 01/14] remote.c: drop default_remote_name variable

[Jeff King]

When we read the remote config from disk, we update a
default_remote_name variable if we see branch.*.remote
config for the current branch. This isn't wrong, or even all
that complicated, but it is a bit simpler (because it
reduces our overall state) to just lazily compute the
default when we need it.

The ulterior motive here is that the push config uses a
similar structure, and _is_ much more complicated as a
result. That will be simplified in a future patch, and it's
more readable if the logic for remotes and push-remotes
matches.

Note that we also used default_remote_name as a signal that
the remote config has been loaded; after this patch, we now
use an explicit flag.

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/remote.c b/remote.c
index 68901b0..bec8b31 100644
--- a/remote.c
+++ b/remote.c
@@ -49,10 +49,8 @@ static int branches_alloc;
 static int branches_nr;
 
 static struct branch *current_branch;
-static const char *default_remote_name;
 static const char *branch_pushremote_name;
 static const char *pushremote_name;
-static int explicit_default_remote_name;
 
 static struct rewrites rewrites;
 static struct rewrites rewrites_push;
@@ -367,12 +365,7 @@ static int handle_config(const char *key, const char *value, void *cb)
 			return 0;
 		branch = make_branch(name, subkey - name);
 		if (!strcmp(subkey, ".remote")) {
-			if (git_config_string(&branch->remote_name, key, value))
-				return -1;
-			if (branch == current_branch) {
-				default_remote_name = branch->remote_name;
-				explicit_default_remote_name = 1;
-			}
+			return git_config_string(&branch->remote_name, key, value);
 		} else if (!strcmp(subkey, ".pushremote")) {
 			if (branch == current_branch)
 				if (git_config_string(&branch_pushremote_name, key, value))
@@ -501,12 +494,15 @@ static void alias_all_urls(void)
 
 static void read_config(void)
 {
+	static int loaded;
 	unsigned char sha1[20];
 	const char *head_ref;
 	int flag;
-	if (default_remote_name) /* did this already */
+
+	if (loaded)
 		return;
-	default_remote_name = "origin";
+	loaded = 1;
+
 	current_branch = NULL;
 	head_ref = resolve_ref_unsafe("HEAD", 0, sha1, &flag);
 	if (head_ref && (flag & REF_ISSYMREF) &&
@@ -708,8 +704,11 @@ static struct remote *remote_get_1(const char *name, const char *pushremote_name
 			name = pushremote_name;
 			name_given = 1;
 		} else {
-			name = default_remote_name;
-			name_given = explicit_default_remote_name;
+			if (current_branch && current_branch->remote_name) {
+				name = current_branch->remote_name;
+				name_given = 1;
+			} else
+				name = "origin";
 		}
 	}
 
-- 
2.4.1.528.g00591e3

[PATCH v3 02/14] remote.c: refactor setup of branch->merge list

[Jeff King]

When we call branch_get() to lookup or create a "struct
branch", we make sure the "merge" field is filled in so that
callers can access it. But the conditions under which we do
so are a little confusing, and can lead to two funny
situations:

  1. If there's no branch.*.remote config, we cannot provide
     branch->merge (because it is really just an application
     of branch.*.merge to our remote's refspecs). But
     branch->merge_nr may be non-zero, leading callers to be
     believe they can access branch->merge (e.g., in
     branch_merge_matches and elsewhere).

     It doesn't look like this can cause a segfault in
     practice, as most code paths dealing with merge config
     will bail early if there is no remote defined. But it's
     a bit of a dangerous construct.

     We can fix this by setting merge_nr to "0" explicitly
     when we realize that we have no merge config. Note that
     merge_nr also counts the "merge_name" fields (which we
     _do_ have; that's how merge_nr got incremented), so we
     will "lose" access to them, in the sense that we forget
     how many we had. But no callers actually care; we use
     merge_name only while iteratively reading the config,
     and then convert it to the final "merge" form the first
     time somebody calls branch_get().

  2. We set up the "merge" field every time branch_get is
     called, even if it has already been done. This leaks
     memory.

     It's not a big deal in practice, since most code paths
     will access only one branch, or perhaps each branch
     only one time. But if you want to be pathological, you
     can leak arbitrary memory with:

       yes @{upstream} | head -1000 | git rev-list --stdin

     We can fix this by skipping setup when branch->merge is
     already non-NULL.

In addition to those two fixes, this patch pushes the "do we
need to setup merge?" logic down into set_merge, where it is
a bit easier to follow.

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/remote.c b/remote.c
index bec8b31..ac17e66 100644
--- a/remote.c
+++ b/remote.c
@@ -1636,6 +1636,19 @@ static void set_merge(struct branch *ret)
 	unsigned char sha1[20];
 	int i;
 
+	if (!ret)
+		return; /* no branch */
+	if (ret->merge)
+		return; /* already run */
+	if (!ret->remote_name || !ret->merge_nr) {
+		/*
+		 * no merge config; let's make sure we don't confuse callers
+		 * with a non-zero merge_nr but a NULL merge
+		 */
+		ret->merge_nr = 0;
+		return;
+	}
+
 	ret->merge = xcalloc(ret->merge_nr, sizeof(*ret->merge));
 	for (i = 0; i < ret->merge_nr; i++) {
 		ret->merge[i] = xcalloc(1, sizeof(**ret->merge));
@@ -1660,11 +1673,9 @@ struct branch *branch_get(const char *name)
 		ret = current_branch;
 	else
 		ret = make_branch(name, 0);
-	if (ret && ret->remote_name) {
+	if (ret && ret->remote_name)
 		ret->remote = remote_get(ret->remote_name);
-		if (ret->merge_nr)
-			set_merge(ret);
-	}
+	set_merge(ret);
 	return ret;
 }
 
-- 
2.4.1.528.g00591e3

[PATCH v3 03/14] remote.c: drop "remote" pointer from "struct branch"

[Jeff King]

When we create each branch struct, we fill in the
"remote_name" field from the config, and then fill in the
actual "remote" field (with a "struct remote") based on that
name. However, it turns out that nobody really cares about
the latter field. The only two sites that access it at all
are:

  1. git-merge, which uses it to notice when the branch does
     not have a remote defined. But we can easily replace this
     with looking at remote_name instead.

  2. remote.c itself, when setting up the @{upstream} merge
     config. But we don't need to save the "remote" in the
     "struct branch" for that; we can just look it up for
     the duration of the operation.

So there is no need to have both fields; they are redundant
with each other (the struct remote contains the name, or you
can look up the struct from the name). It would be nice to
simplify this, especially as we are going to add matching
pushremote config in a future patch (and it would be nice to
keep them consistent).

So which one do we keep and which one do we get rid of?

If we had a lot of callers accessing the struct, it would be
more efficient to keep it (since you have to do a lookup to
go from the name to the struct, but not vice versa). But we
don't have a lot of callers; we have exactly one, so
efficiency doesn't matter. We can decide this based on
simplicity and readability.

And the meaning of the struct value is somewhat unclear. Is
it always the remote matching remote_name? If remote_name is
NULL (i.e., no per-branch config), does the struct fall back
to the "origin" remote, or is it also NULL? These questions
will get even more tricky with pushremotes, whose fallback
behavior is more complicated. So let's just store the name,
which pretty clearly represents the branch.*.remote config.
Any lookup or fallback behavior can then be implemented in
helper functions.

Signed-off-by: Jeff King <peff@peff.net>
---
 Documentation/technical/api-remote.txt | 4 ----
 builtin/merge.c                        | 2 +-
 remote.c                               | 7 ++++---
 remote.h                               | 1 -
 4 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/Documentation/technical/api-remote.txt b/Documentation/technical/api-remote.txt
index 5d245aa..2cfdd22 100644
--- a/Documentation/technical/api-remote.txt
+++ b/Documentation/technical/api-remote.txt
@@ -97,10 +97,6 @@ It contains:
 
 	The name of the remote listed in the configuration.
 
-`remote`::
-
-	The struct remote for that remote.
-
 `merge_name`::
 
 	An array of the "merge" lines in the configuration.
diff --git a/builtin/merge.c b/builtin/merge.c
index f89f60e..85c54dc 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -933,7 +933,7 @@ static int setup_with_upstream(const char ***argv)
 
 	if (!branch)
 		die(_("No current branch."));
-	if (!branch->remote)
+	if (!branch->remote_name)
 		die(_("No remote for the current branch."));
 	if (!branch->merge_nr)
 		die(_("No default upstream defined for the current branch."));
diff --git a/remote.c b/remote.c
index ac17e66..c298a43 100644
--- a/remote.c
+++ b/remote.c
@@ -1632,6 +1632,7 @@ void set_ref_status_for_push(struct ref *remote_refs, int send_mirror,
 
 static void set_merge(struct branch *ret)
 {
+	struct remote *remote;
 	char *ref;
 	unsigned char sha1[20];
 	int i;
@@ -1649,11 +1650,13 @@ static void set_merge(struct branch *ret)
 		return;
 	}
 
+	remote = remote_get(ret->remote_name);
+
 	ret->merge = xcalloc(ret->merge_nr, sizeof(*ret->merge));
 	for (i = 0; i < ret->merge_nr; i++) {
 		ret->merge[i] = xcalloc(1, sizeof(**ret->merge));
 		ret->merge[i]->src = xstrdup(ret->merge_name[i]);
-		if (!remote_find_tracking(ret->remote, ret->merge[i]) ||
+		if (!remote_find_tracking(remote, ret->merge[i]) ||
 		    strcmp(ret->remote_name, "."))
 			continue;
 		if (dwim_ref(ret->merge_name[i], strlen(ret->merge_name[i]),
@@ -1673,8 +1676,6 @@ struct branch *branch_get(const char *name)
 		ret = current_branch;
 	else
 		ret = make_branch(name, 0);
-	if (ret && ret->remote_name)
-		ret->remote = remote_get(ret->remote_name);
 	set_merge(ret);
 	return ret;
 }
diff --git a/remote.h b/remote.h
index 02d66ce..4bb6672 100644
--- a/remote.h
+++ b/remote.h
@@ -203,7 +203,6 @@ struct branch {
 	const char *refname;
 
 	const char *remote_name;
-	struct remote *remote;
 
 	const char **merge_name;
 	struct refspec **merge;
-- 
2.4.1.528.g00591e3

[PATCH v3 04/14] remote.c: hoist branch.*.remote lookup out of remote_get_1

[Jeff King]

We'll want to use this logic as a fallback when looking up
the pushremote, so let's pull it out into its own function.

We don't technically need to make this available outside of
remote.c, but doing so will provide a consistent API with
pushremote_for_branch, which we will add later.

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 21 ++++++++++++++-------
 remote.h |  1 +
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/remote.c b/remote.c
index c298a43..0d2976b 100644
--- a/remote.c
+++ b/remote.c
@@ -692,6 +692,18 @@ static int valid_remote_nick(const char *name)
 	return !strchr(name, '/'); /* no slash */
 }
 
+const char *remote_for_branch(struct branch *branch, int *explicit)
+{
+	if (branch && branch->remote_name) {
+		if (explicit)
+			*explicit = 1;
+		return branch->remote_name;
+	}
+	if (explicit)
+		*explicit = 0;
+	return "origin";
+}
+
 static struct remote *remote_get_1(const char *name, const char *pushremote_name)
 {
 	struct remote *ret;
@@ -703,13 +715,8 @@ static struct remote *remote_get_1(const char *name, const char *pushremote_name
 		if (pushremote_name) {
 			name = pushremote_name;
 			name_given = 1;
-		} else {
-			if (current_branch && current_branch->remote_name) {
-				name = current_branch->remote_name;
-				name_given = 1;
-			} else
-				name = "origin";
-		}
+		} else
+			name = remote_for_branch(current_branch, &name_given);
 	}
 
 	ret = make_remote(name, 0);
diff --git a/remote.h b/remote.h
index 4bb6672..2a7e7a6 100644
--- a/remote.h
+++ b/remote.h
@@ -211,6 +211,7 @@ struct branch {
 };
 
 struct branch *branch_get(const char *name);
+const char *remote_for_branch(struct branch *branch, int *explicit);
 
 int branch_has_merge_config(struct branch *branch);
 int branch_merge_matches(struct branch *, int n, const char *);
-- 
2.4.1.528.g00591e3

[PATCH v3 05/14] remote.c: provide per-branch pushremote name

[Jeff King]

When remote.c loads its config, it records the
branch.*.pushremote for the current branch along with the
global remote.pushDefault value, and then binds them into a
single value: the default push for the current branch. We
then pass this value (which may be NULL) to remote_get_1
when looking up a remote for push.

This has a few downsides:

  1. It's confusing. The early-binding of the "current
     value" led to bugs like the one fixed by 98b406f
     (remote: handle pushremote config in any order,
     2014-02-24). And the fact that pushremotes fall back to
     ordinary remotes is not explicit at all; it happens
     because remote_get_1 cannot tell the difference between
     "we are not asking for the push remote" and "there is
     no push remote configured".

  2. It throws away intermediate data. After read_config()
     finishes, we have no idea what the value of
     remote.pushDefault was, because the string has been
     overwritten by the current branch's
     branch.*.pushremote.

  3. It doesn't record other data. We don't note the
     branch.*.pushremote value for anything but the current
     branch.

Let's make this more like the fetch-remote config. We'll
record the pushremote for each branch, and then explicitly
compute the correct remote for the current branch at the
time of reading.

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 40 ++++++++++++++++++++++------------------
 remote.h |  2 ++
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/remote.c b/remote.c
index 0d2976b..a91d063 100644
--- a/remote.c
+++ b/remote.c
@@ -49,7 +49,6 @@ static int branches_alloc;
 static int branches_nr;
 
 static struct branch *current_branch;
-static const char *branch_pushremote_name;
 static const char *pushremote_name;
 
 static struct rewrites rewrites;
@@ -367,9 +366,7 @@ static int handle_config(const char *key, const char *value, void *cb)
 		if (!strcmp(subkey, ".remote")) {
 			return git_config_string(&branch->remote_name, key, value);
 		} else if (!strcmp(subkey, ".pushremote")) {
-			if (branch == current_branch)
-				if (git_config_string(&branch_pushremote_name, key, value))
-					return -1;
+			return git_config_string(&branch->pushremote_name, key, value);
 		} else if (!strcmp(subkey, ".merge")) {
 			if (!value)
 				return config_error_nonbool(key);
@@ -510,10 +507,6 @@ static void read_config(void)
 		current_branch = make_branch(head_ref, 0);
 	}
 	git_config(handle_config, NULL);
-	if (branch_pushremote_name) {
-		free((char *)pushremote_name);
-		pushremote_name = branch_pushremote_name;
-	}
 	alias_all_urls();
 }
 
@@ -704,20 +697,31 @@ const char *remote_for_branch(struct branch *branch, int *explicit)
 	return "origin";
 }
 
-static struct remote *remote_get_1(const char *name, const char *pushremote_name)
+const char *pushremote_for_branch(struct branch *branch, int *explicit)
+{
+	if (branch && branch->pushremote_name) {
+		if (explicit)
+			*explicit = 1;
+		return branch->pushremote_name;
+	}
+	if (pushremote_name) {
+		if (explicit)
+			*explicit = 1;
+		return pushremote_name;
+	}
+	return remote_for_branch(branch, explicit);
+}
+
+static struct remote *remote_get_1(const char *name,
+				   const char *(*get_default)(struct branch *, int *))
 {
 	struct remote *ret;
 	int name_given = 0;
 
 	if (name)
 		name_given = 1;
-	else {
-		if (pushremote_name) {
-			name = pushremote_name;
-			name_given = 1;
-		} else
-			name = remote_for_branch(current_branch, &name_given);
-	}
+	else
+		name = get_default(current_branch, &name_given);
 
 	ret = make_remote(name, 0);
 	if (valid_remote_nick(name)) {
@@ -738,13 +742,13 @@ static struct remote *remote_get_1(const char *name, const char *pushremote_name
 struct remote *remote_get(const char *name)
 {
 	read_config();
-	return remote_get_1(name, NULL);
+	return remote_get_1(name, remote_for_branch);
 }
 
 struct remote *pushremote_get(const char *name)
 {
 	read_config();
-	return remote_get_1(name, pushremote_name);
+	return remote_get_1(name, pushremote_for_branch);
 }
 
 int remote_is_configured(const char *name)
diff --git a/remote.h b/remote.h
index 2a7e7a6..30a11da 100644
--- a/remote.h
+++ b/remote.h
@@ -203,6 +203,7 @@ struct branch {
 	const char *refname;
 
 	const char *remote_name;
+	const char *pushremote_name;
 
 	const char **merge_name;
 	struct refspec **merge;
@@ -212,6 +213,7 @@ struct branch {
 
 struct branch *branch_get(const char *name);
 const char *remote_for_branch(struct branch *branch, int *explicit);
+const char *pushremote_for_branch(struct branch *branch, int *explicit);
 
 int branch_has_merge_config(struct branch *branch);
 int branch_merge_matches(struct branch *, int n, const char *);
-- 
2.4.1.528.g00591e3

[PATCH v3 06/14] remote.c: hoist read_config into remote_get_1

[Jeff King]

Before the previous commit, we had to make sure that
read_config() was called before entering remote_get_1,
because we needed to pass pushremote_name by value. But now
that we pass a function, we can let remote_get_1 handle
loading the config itself, turning our wrappers into true
one-liners.

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/remote.c b/remote.c
index a91d063..e6b29b3 100644
--- a/remote.c
+++ b/remote.c
@@ -718,6 +718,8 @@ static struct remote *remote_get_1(const char *name,
 	struct remote *ret;
 	int name_given = 0;
 
+	read_config();
+
 	if (name)
 		name_given = 1;
 	else
@@ -741,13 +743,11 @@ static struct remote *remote_get_1(const char *name,
 
 struct remote *remote_get(const char *name)
 {
-	read_config();
 	return remote_get_1(name, remote_for_branch);
 }
 
 struct remote *pushremote_get(const char *name)
 {
-	read_config();
 	return remote_get_1(name, pushremote_for_branch);
 }
 
-- 
2.4.1.528.g00591e3

[PATCH v3 07/14] remote.c: introduce branch_get_upstream helper

[Jeff King]

All of the information needed to find the @{upstream} of a
branch is included in the branch struct, but callers have to
navigate a series of possible-NULL values to get there.
Let's wrap that logic up in an easy-to-read helper.

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/branch.c       |  8 +++-----
 builtin/for-each-ref.c |  5 ++---
 builtin/log.c          |  7 ++-----
 remote.c               | 12 +++++++++---
 remote.h               |  7 +++++++
 5 files changed, 23 insertions(+), 16 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 258fe2f..1eb6215 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -123,14 +123,12 @@ static int branch_merged(int kind, const char *name,
 
 	if (kind == REF_LOCAL_BRANCH) {
 		struct branch *branch = branch_get(name);
+		const char *upstream = branch_get_upstream(branch);
 		unsigned char sha1[20];
 
-		if (branch &&
-		    branch->merge &&
-		    branch->merge[0] &&
-		    branch->merge[0]->dst &&
+		if (upstream &&
 		    (reference_name = reference_name_to_free =
-		     resolve_refdup(branch->merge[0]->dst, RESOLVE_REF_READING,
+		     resolve_refdup(upstream, RESOLVE_REF_READING,
 				    sha1, NULL)) != NULL)
 			reference_rev = lookup_commit_reference(sha1);
 	}
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 83f9cf9..dc2a201 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -664,10 +664,9 @@ static void populate_value(struct refinfo *ref)
 				continue;
 			branch = branch_get(ref->refname + 11);
 
-			if (!branch || !branch->merge || !branch->merge[0] ||
-			    !branch->merge[0]->dst)
+			refname = branch_get_upstream(branch);
+			if (!refname)
 				continue;
-			refname = branch->merge[0]->dst;
 		} else if (starts_with(name, "color:")) {
 			char color[COLOR_MAXLEN] = "";
 
diff --git a/builtin/log.c b/builtin/log.c
index dd8f3fc..fb61c08 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1632,16 +1632,13 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
 		break;
 	default:
 		current_branch = branch_get(NULL);
-		if (!current_branch || !current_branch->merge
-					|| !current_branch->merge[0]
-					|| !current_branch->merge[0]->dst) {
+		upstream = branch_get_upstream(current_branch);
+		if (!upstream) {
 			fprintf(stderr, _("Could not find a tracked"
 					" remote branch, please"
 					" specify <upstream> manually.\n"));
 			usage_with_options(cherry_usage, options);
 		}
-
-		upstream = current_branch->merge[0]->dst;
 	}
 
 	init_revisions(&revs, prefix);
diff --git a/remote.c b/remote.c
index e6b29b3..dca3442 100644
--- a/remote.c
+++ b/remote.c
@@ -1705,6 +1705,13 @@ int branch_merge_matches(struct branch *branch,
 	return refname_match(branch->merge[i]->src, refname);
 }
 
+const char *branch_get_upstream(struct branch *branch)
+{
+	if (!branch || !branch->merge || !branch->merge[0])
+		return NULL;
+	return branch->merge[0]->dst;
+}
+
 static int ignore_symref_update(const char *refname)
 {
 	unsigned char sha1[20];
@@ -1914,12 +1921,11 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	int rev_argc;
 
 	/* Cannot stat unless we are marked to build on top of somebody else. */
-	if (!branch ||
-	    !branch->merge || !branch->merge[0] || !branch->merge[0]->dst)
+	base = branch_get_upstream(branch);
+	if (!base)
 		return 0;
 
 	/* Cannot stat if what we used to build on no longer exists */
-	base = branch->merge[0]->dst;
 	if (read_ref(base, sha1))
 		return -1;
 	theirs = lookup_commit_reference(sha1);
diff --git a/remote.h b/remote.h
index 30a11da..d968952 100644
--- a/remote.h
+++ b/remote.h
@@ -218,6 +218,13 @@ const char *pushremote_for_branch(struct branch *branch, int *explicit);
 int branch_has_merge_config(struct branch *branch);
 int branch_merge_matches(struct branch *, int n, const char *);
 
+/**
+ * Return the fully-qualified refname of the tracking branch for `branch`.
+ * I.e., what "branch@{upstream}" would give you. Returns NULL if no
+ * upstream is defined.
+ */
+const char *branch_get_upstream(struct branch *branch);
+
 /* Flags to match_refs. */
 enum match_refs_flags {
 	MATCH_REFS_NONE		= 0,
-- 
2.4.1.528.g00591e3

[PATCH v3 08/14] remote.c: report specific errors from branch_get_upstream

[Jeff King]

When the previous commit introduced the branch_get_upstream
helper, there was one call-site that could not be converted:
the one in sha1_name.c, which gives detailed error messages
for each possible failure.

Let's teach the helper to optionally report these specific
errors. This lets us convert another callsite, and means we
can use the helper in other locations that want to give the
same error messages.

The logic and error messages come straight from sha1_name.c,
with the exception that we start each error with a lowercase
letter, as is our usual style (note that a few tests need
updated as a result).

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/branch.c              |  2 +-
 builtin/for-each-ref.c        |  2 +-
 builtin/log.c                 |  2 +-
 remote.c                      | 33 +++++++++++++++++++++++++++++----
 remote.h                      |  6 +++++-
 sha1_name.c                   | 25 +++++++------------------
 t/t1507-rev-parse-upstream.sh |  8 ++++----
 7 files changed, 48 insertions(+), 30 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 1eb6215..cc55ff2 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -123,7 +123,7 @@ static int branch_merged(int kind, const char *name,
 
 	if (kind == REF_LOCAL_BRANCH) {
 		struct branch *branch = branch_get(name);
-		const char *upstream = branch_get_upstream(branch);
+		const char *upstream = branch_get_upstream(branch, NULL);
 		unsigned char sha1[20];
 
 		if (upstream &&
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index dc2a201..18d209b 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -664,7 +664,7 @@ static void populate_value(struct refinfo *ref)
 				continue;
 			branch = branch_get(ref->refname + 11);
 
-			refname = branch_get_upstream(branch);
+			refname = branch_get_upstream(branch, NULL);
 			if (!refname)
 				continue;
 		} else if (starts_with(name, "color:")) {
diff --git a/builtin/log.c b/builtin/log.c
index fb61c08..6faeb82 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -1632,7 +1632,7 @@ int cmd_cherry(int argc, const char **argv, const char *prefix)
 		break;
 	default:
 		current_branch = branch_get(NULL);
-		upstream = branch_get_upstream(current_branch);
+		upstream = branch_get_upstream(current_branch, NULL);
 		if (!upstream) {
 			fprintf(stderr, _("Could not find a tracked"
 					" remote branch, please"
diff --git a/remote.c b/remote.c
index dca3442..1b7051a 100644
--- a/remote.c
+++ b/remote.c
@@ -1705,10 +1705,35 @@ int branch_merge_matches(struct branch *branch,
 	return refname_match(branch->merge[i]->src, refname);
 }
 
-const char *branch_get_upstream(struct branch *branch)
+__attribute((format (printf,2,3)))
+static const char *error_buf(struct strbuf *err, const char *fmt, ...)
 {
-	if (!branch || !branch->merge || !branch->merge[0])
-		return NULL;
+	if (err) {
+		va_list ap;
+		va_start(ap, fmt);
+		strbuf_vaddf(err, fmt, ap);
+		va_end(ap);
+	}
+	return NULL;
+}
+
+const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
+{
+	if (!branch)
+		return error_buf(err, _("HEAD does not point to a branch"));
+	if (!branch->merge || !branch->merge[0] || !branch->merge[0]->dst) {
+		if (!ref_exists(branch->refname))
+			return error_buf(err, _("no such branch: '%s'"),
+					 branch->name);
+		if (!branch->merge)
+			return error_buf(err,
+					 _("no upstream configured for branch '%s'"),
+					 branch->name);
+		return error_buf(err,
+				 _("upstream branch '%s' not stored as a remote-tracking branch"),
+				 branch->merge[0]->src);
+	}
+
 	return branch->merge[0]->dst;
 }
 
@@ -1921,7 +1946,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	int rev_argc;
 
 	/* Cannot stat unless we are marked to build on top of somebody else. */
-	base = branch_get_upstream(branch);
+	base = branch_get_upstream(branch, NULL);
 	if (!base)
 		return 0;
 
diff --git a/remote.h b/remote.h
index d968952..03ca005 100644
--- a/remote.h
+++ b/remote.h
@@ -222,8 +222,12 @@ int branch_merge_matches(struct branch *, int n, const char *);
  * Return the fully-qualified refname of the tracking branch for `branch`.
  * I.e., what "branch@{upstream}" would give you. Returns NULL if no
  * upstream is defined.
+ *
+ * If `err` is not NULL and no upstream is defined, a more specific error
+ * message is recorded there (if the function does not return NULL, then
+ * `err` is not touched).
  */
-const char *branch_get_upstream(struct branch *branch);
+const char *branch_get_upstream(struct branch *branch, struct strbuf *err);
 
 /* Flags to match_refs. */
 enum match_refs_flags {
diff --git a/sha1_name.c b/sha1_name.c
index 6d10f05..461157a 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -1059,27 +1059,16 @@ static const char *get_upstream_branch(const char *branch_buf, int len)
 {
 	char *branch = xstrndup(branch_buf, len);
 	struct branch *upstream = branch_get(*branch ? branch : NULL);
+	struct strbuf err = STRBUF_INIT;
+	const char *ret;
 
-	/*
-	 * Upstream can be NULL only if branch refers to HEAD and HEAD
-	 * points to something different than a branch.
-	 */
-	if (!upstream)
-		die(_("HEAD does not point to a branch"));
-	if (!upstream->merge || !upstream->merge[0]->dst) {
-		if (!ref_exists(upstream->refname))
-			die(_("No such branch: '%s'"), branch);
-		if (!upstream->merge) {
-			die(_("No upstream configured for branch '%s'"),
-				upstream->name);
-		}
-		die(
-			_("Upstream branch '%s' not stored as a remote-tracking branch"),
-			upstream->merge[0]->src);
-	}
 	free(branch);
 
-	return upstream->merge[0]->dst;
+	ret = branch_get_upstream(upstream, &err);
+	if (!ret)
+		die("%s", err.buf);
+
+	return ret;
 }
 
 static int interpret_upstream_mark(const char *name, int namelen,
diff --git a/t/t1507-rev-parse-upstream.sh b/t/t1507-rev-parse-upstream.sh
index 1978947..46ef1f2 100755
--- a/t/t1507-rev-parse-upstream.sh
+++ b/t/t1507-rev-parse-upstream.sh
@@ -150,7 +150,7 @@ test_expect_success 'branch@{u} works when tracking a local branch' '
 
 test_expect_success 'branch@{u} error message when no upstream' '
 	cat >expect <<-EOF &&
-	fatal: No upstream configured for branch ${sq}non-tracking${sq}
+	fatal: no upstream configured for branch ${sq}non-tracking${sq}
 	EOF
 	error_message non-tracking@{u} 2>actual &&
 	test_i18ncmp expect actual
@@ -158,7 +158,7 @@ test_expect_success 'branch@{u} error message when no upstream' '
 
 test_expect_success '@{u} error message when no upstream' '
 	cat >expect <<-EOF &&
-	fatal: No upstream configured for branch ${sq}master${sq}
+	fatal: no upstream configured for branch ${sq}master${sq}
 	EOF
 	test_must_fail git rev-parse --verify @{u} 2>actual &&
 	test_i18ncmp expect actual
@@ -166,7 +166,7 @@ test_expect_success '@{u} error message when no upstream' '
 
 test_expect_success 'branch@{u} error message with misspelt branch' '
 	cat >expect <<-EOF &&
-	fatal: No such branch: ${sq}no-such-branch${sq}
+	fatal: no such branch: ${sq}no-such-branch${sq}
 	EOF
 	error_message no-such-branch@{u} 2>actual &&
 	test_i18ncmp expect actual
@@ -183,7 +183,7 @@ test_expect_success '@{u} error message when not on a branch' '
 
 test_expect_success 'branch@{u} error message if upstream branch not fetched' '
 	cat >expect <<-EOF &&
-	fatal: Upstream branch ${sq}refs/heads/side${sq} not stored as a remote-tracking branch
+	fatal: upstream branch ${sq}refs/heads/side${sq} not stored as a remote-tracking branch
 	EOF
 	error_message bad-upstream@{u} 2>actual &&
 	test_i18ncmp expect actual
-- 
2.4.1.528.g00591e3

[PATCH v3 09/14] remote.c: add branch_get_push

[Jeff King]

In a triangular workflow, the place you pull from and the
place you push to may be different. As we have
branch_get_upstream for the former, this patch adds
branch_get_push for the latter (and as the former implements
@{upstream}, so will this implement @{push} in a future
patch).

Note that the memory-handling for the return value bears
some explanation. Some code paths require allocating a new
string, and some let us return an existing string. We should
provide a consistent interface to the caller, so it knows
whether to free the result or not.

We could do so by xstrdup-ing any existing strings, and
having the caller always free. But that makes us
inconsistent with branch_get_upstream, so we would prefer to
simply take ownership of the resulting string. We do so by
storing it inside the "struct branch", just as we do with
the upstream refname (in that case we compute it when the
branch is created, but there's no reason not to just fill
it in lazily in this case).

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 remote.h | 10 ++++++++
 2 files changed, 95 insertions(+)

diff --git a/remote.c b/remote.c
index 1b7051a..be45a39 100644
--- a/remote.c
+++ b/remote.c
@@ -1737,6 +1737,91 @@ const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
 	return branch->merge[0]->dst;
 }
 
+static const char *tracking_for_push_dest(struct remote *remote,
+					  const char *refname,
+					  struct strbuf *err)
+{
+	char *ret;
+
+	ret = apply_refspecs(remote->fetch, remote->fetch_refspec_nr, refname);
+	if (!ret)
+		return error_buf(err,
+				 _("push destination '%s' on remote '%s' has no local tracking branch"),
+				 refname, remote->name);
+	return ret;
+}
+
+static const char *branch_get_push_1(struct branch *branch, struct strbuf *err)
+{
+	struct remote *remote;
+
+	if (!branch)
+		return error_buf(err, _("HEAD does not point to a branch"));
+
+	remote = remote_get(pushremote_for_branch(branch, NULL));
+	if (!remote)
+		return error_buf(err,
+				 _("branch '%s' has no remote for pushing"),
+				 branch->name);
+
+	if (remote->push_refspec_nr) {
+		char *dst;
+		const char *ret;
+
+		dst = apply_refspecs(remote->push, remote->push_refspec_nr,
+				     branch->refname);
+		if (!dst)
+			return error_buf(err,
+					 _("push refspecs for '%s' do not include '%s'"),
+					 remote->name, branch->name);
+
+		ret = tracking_for_push_dest(remote, dst, err);
+		free(dst);
+		return ret;
+	}
+
+	if (remote->mirror)
+		return tracking_for_push_dest(remote, branch->refname, err);
+
+	switch (push_default) {
+	case PUSH_DEFAULT_NOTHING:
+		return error_buf(err, _("push has no destination (push.default is 'nothing')"));
+
+	case PUSH_DEFAULT_MATCHING:
+	case PUSH_DEFAULT_CURRENT:
+		return tracking_for_push_dest(remote, branch->refname, err);
+
+	case PUSH_DEFAULT_UPSTREAM:
+		return branch_get_upstream(branch, err);
+
+	case PUSH_DEFAULT_UNSPECIFIED:
+	case PUSH_DEFAULT_SIMPLE:
+		{
+			const char *up, *cur;
+
+			up = branch_get_upstream(branch, err);
+			if (!up)
+				return NULL;
+			cur = tracking_for_push_dest(remote, branch->refname, err);
+			if (!cur)
+				return NULL;
+			if (strcmp(cur, up))
+				return error_buf(err,
+						 _("cannot resolve 'simple' push to a single destination"));
+			return cur;
+		}
+	}
+
+	die("BUG: unhandled push situation");
+}
+
+const char *branch_get_push(struct branch *branch, struct strbuf *err)
+{
+	if (!branch->push_tracking_ref)
+		branch->push_tracking_ref = branch_get_push_1(branch, err);
+	return branch->push_tracking_ref;
+}
+
 static int ignore_symref_update(const char *refname)
 {
 	unsigned char sha1[20];
diff --git a/remote.h b/remote.h
index 03ca005..3326f2b 100644
--- a/remote.h
+++ b/remote.h
@@ -209,6 +209,8 @@ struct branch {
 	struct refspec **merge;
 	int merge_nr;
 	int merge_alloc;
+
+	const char *push_tracking_ref;
 };
 
 struct branch *branch_get(const char *name);
@@ -229,6 +231,14 @@ int branch_merge_matches(struct branch *, int n, const char *);
  */
 const char *branch_get_upstream(struct branch *branch, struct strbuf *err);
 
+/**
+ * Return the tracking branch that corresponds to the ref we would push to
+ * given a bare `git push` while `branch` is checked out.
+ *
+ * The return value and `err` conventions match those of `branch_get_upstream`.
+ */
+const char *branch_get_push(struct branch *branch, struct strbuf *err);
+
 /* Flags to match_refs. */
 enum match_refs_flags {
 	MATCH_REFS_NONE		= 0,
-- 
2.4.1.528.g00591e3

[PATCH v3 10/14] sha1_name: refactor upstream_mark

[Jeff King]

We will be adding new mark types in the future, so separate
the suffix data from the logic.

Signed-off-by: Jeff King <peff@peff.net>
---
 sha1_name.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 461157a..1005f45 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -415,12 +415,12 @@ static int ambiguous_path(const char *path, int len)
 	return slash;
 }
 
-static inline int upstream_mark(const char *string, int len)
+static inline int at_mark(const char *string, int len,
+			  const char **suffix, int nr)
 {
-	const char *suffix[] = { "@{upstream}", "@{u}" };
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(suffix); i++) {
+	for (i = 0; i < nr; i++) {
 		int suffix_len = strlen(suffix[i]);
 		if (suffix_len <= len
 		    && !memcmp(string, suffix[i], suffix_len))
@@ -429,6 +429,12 @@ static inline int upstream_mark(const char *string, int len)
 	return 0;
 }
 
+static inline int upstream_mark(const char *string, int len)
+{
+	const char *suffix[] = { "@{upstream}", "@{u}" };
+	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
+}
+
 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 
-- 
2.4.1.528.g00591e3

[PATCH v3 11/14] sha1_name: refactor interpret_upstream_mark

[Jeff King]

Now that most of the logic for our local get_upstream_branch
has been pushed into the generic branch_get_upstream, we can
fold the remainder into interpret_upstream_mark.

Furthermore, what remains is generic to any branch-related
"@{foo}" we might add in the future, and there's enough
boilerplate that we'd like to reuse it. Let's parameterize
the two operations (parsing the mark and computing its
value) so that we can reuse this for "@{push}" in the near
future.

Signed-off-by: Jeff King <peff@peff.net>
---
 sha1_name.c | 44 +++++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 1005f45..506e0c9 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -1061,35 +1061,36 @@ static void set_shortened_ref(struct strbuf *buf, const char *ref)
 	free(s);
 }
 
-static const char *get_upstream_branch(const char *branch_buf, int len)
-{
-	char *branch = xstrndup(branch_buf, len);
-	struct branch *upstream = branch_get(*branch ? branch : NULL);
-	struct strbuf err = STRBUF_INIT;
-	const char *ret;
-
-	free(branch);
-
-	ret = branch_get_upstream(upstream, &err);
-	if (!ret)
-		die("%s", err.buf);
-
-	return ret;
-}
-
-static int interpret_upstream_mark(const char *name, int namelen,
-				   int at, struct strbuf *buf)
+static int interpret_branch_mark(const char *name, int namelen,
+				 int at, struct strbuf *buf,
+				 int (*get_mark)(const char *, int),
+				 const char *(*get_data)(struct branch *,
+							 struct strbuf *))
 {
 	int len;
+	struct branch *branch;
+	struct strbuf err = STRBUF_INIT;
+	const char *value;
 
-	len = upstream_mark(name + at, namelen - at);
+	len = get_mark(name + at, namelen - at);
 	if (!len)
 		return -1;
 
 	if (memchr(name, ':', at))
 		return -1;
 
-	set_shortened_ref(buf, get_upstream_branch(name, at));
+	if (at) {
+		char *name_str = xmemdupz(name, at);
+		branch = branch_get(name_str);
+		free(name_str);
+	} else
+		branch = branch_get(NULL);
+
+	value = get_data(branch, &err);
+	if (!value)
+		die("%s", err.buf);
+
+	set_shortened_ref(buf, value);
 	return len + at;
 }
 
@@ -1140,7 +1141,8 @@ int interpret_branch_name(const char *name, int namelen, struct strbuf *buf)
 		if (len > 0)
 			return reinterpret(name, namelen, len, buf);
 
-		len = interpret_upstream_mark(name, namelen, at - name, buf);
+		len = interpret_branch_mark(name, namelen, at - name, buf,
+					    upstream_mark, branch_get_upstream);
 		if (len > 0)
 			return len;
 	}
-- 
2.4.1.528.g00591e3

[PATCH v3 12/14] sha1_name: implement @{push} shorthand

[Jeff King]

In a triangular workflow, each branch may have two distinct
points of interest: the @{upstream} that you normally pull
from, and the destination that you normally push to. There
isn't a shorthand for the latter, but it's useful to have.

For instance, you may want to know which commits you haven't
pushed yet:

  git log @{push}..

Or as a more complicated example, imagine that you normally
pull changes from origin/master (which you set as your
@{upstream}), and push changes to your own personal fork
(e.g., as myfork/topic). You may push to your fork from
multiple machines, requiring you to integrate the changes
from the push destination, rather than upstream. With this
patch, you can just do:

  git rebase @{push}

rather than typing out the full name.

The heavy lifting is all done by branch_get_push; here we
just wire it up to the "@{push}" syntax.

Signed-off-by: Jeff King <peff@peff.net>
---
 Documentation/revisions.txt | 25 ++++++++++++++++++
 sha1_name.c                 | 14 +++++++++-
 t/t1514-rev-parse-push.sh   | 63 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 101 insertions(+), 1 deletion(-)
 create mode 100755 t/t1514-rev-parse-push.sh

diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
index 0796118..d85e303 100644
--- a/Documentation/revisions.txt
+++ b/Documentation/revisions.txt
@@ -98,6 +98,31 @@ some output processing may assume ref names in UTF-8.
   `branch.<name>.merge`).  A missing branchname defaults to the
   current one.
 
+'<branchname>@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
+  The suffix '@\{push}' reports the branch "where we would push to" if
+  `git push` were run while `branchname` was checked out (or the current
+  'HEAD' if no branchname is specified). Since our push destination is
+  in a remote repository, of course, we report the local tracking branch
+  that corresponds to that branch (i.e., something in 'refs/remotes/').
++
+Here's an example to make it more clear:
++
+------------------------------
+$ git config push.default current
+$ git config remote.pushdefault myfork
+$ git checkout -b mybranch origin/master
+
+$ git rev-parse --symbolic-full-name @{upstream}
+refs/remotes/origin/master
+
+$ git rev-parse --symbolic-full-name @{push}
+refs/remotes/myfork/mybranch
+------------------------------
++
+Note in the example that we set up a triangular workflow, where we pull
+from one location and push to another. In a non-triangular workflow,
+'@\{push}' is the same as '@\{upstream}', and there is no need for it.
+
 '<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
   A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
diff --git a/sha1_name.c b/sha1_name.c
index 506e0c9..1096943 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -435,6 +435,12 @@ static inline int upstream_mark(const char *string, int len)
 	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
 }
 
+static inline int push_mark(const char *string, int len)
+{
+	const char *suffix[] = { "@{push}" };
+	return at_mark(string, len, suffix, ARRAY_SIZE(suffix));
+}
+
 static int get_sha1_1(const char *name, int len, unsigned char *sha1, unsigned lookup_flags);
 static int interpret_nth_prior_checkout(const char *name, int namelen, struct strbuf *buf);
 
@@ -482,7 +488,8 @@ static int get_sha1_basic(const char *str, int len, unsigned char *sha1,
 					nth_prior = 1;
 					continue;
 				}
-				if (!upstream_mark(str + at, len - at)) {
+				if (!upstream_mark(str + at, len - at) &&
+				    !push_mark(str + at, len - at)) {
 					reflog_len = (len-1) - (at+2);
 					len = at;
 				}
@@ -1145,6 +1152,11 @@ int interpret_branch_name(const char *name, int namelen, struct strbuf *buf)
 					    upstream_mark, branch_get_upstream);
 		if (len > 0)
 			return len;
+
+		len = interpret_branch_mark(name, namelen, at - name, buf,
+					    push_mark, branch_get_push);
+		if (len > 0)
+			return len;
 	}
 
 	return -1;
diff --git a/t/t1514-rev-parse-push.sh b/t/t1514-rev-parse-push.sh
new file mode 100755
index 0000000..7214f5b
--- /dev/null
+++ b/t/t1514-rev-parse-push.sh
@@ -0,0 +1,63 @@
+#!/bin/sh
+
+test_description='test <branch>@{push} syntax'
+. ./test-lib.sh
+
+resolve () {
+	echo "$2" >expect &&
+	git rev-parse --symbolic-full-name "$1" >actual &&
+	test_cmp expect actual
+}
+
+test_expect_success 'setup' '
+	git init --bare parent.git &&
+	git init --bare other.git &&
+	git remote add origin parent.git &&
+	git remote add other other.git &&
+	test_commit base &&
+	git push origin HEAD &&
+	git branch --set-upstream-to=origin/master master &&
+	git branch --track topic origin/master &&
+	git push origin topic &&
+	git push other topic
+'
+
+test_expect_success '@{push} with default=nothing' '
+	test_config push.default nothing &&
+	test_must_fail git rev-parse master@{push}
+'
+
+test_expect_success '@{push} with default=simple' '
+	test_config push.default simple &&
+	resolve master@{push} refs/remotes/origin/master
+'
+
+test_expect_success 'triangular @{push} fails with default=simple' '
+	test_config push.default simple &&
+	test_must_fail git rev-parse topic@{push}
+'
+
+test_expect_success '@{push} with default=current' '
+	test_config push.default current &&
+	resolve topic@{push} refs/remotes/origin/topic
+'
+
+test_expect_success '@{push} with default=matching' '
+	test_config push.default matching &&
+	resolve topic@{push} refs/remotes/origin/topic
+'
+
+test_expect_success '@{push} with pushremote defined' '
+	test_config push.default current &&
+	test_config branch.topic.pushremote other &&
+	resolve topic@{push} refs/remotes/other/topic
+'
+
+test_expect_success '@{push} with push refspecs' '
+	test_config push.default nothing &&
+	test_config remote.origin.push refs/heads/*:refs/heads/magic/* &&
+	git push &&
+	resolve topic@{push} refs/remotes/origin/magic/topic
+'
+
+test_done
-- 
2.4.1.528.g00591e3

[PATCH v3 13/14] for-each-ref: use skip_prefix instead of starts_with

[Jeff King]

This saves us having to maintain a magic number to skip past
the matched prefix.

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/for-each-ref.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 18d209b..345d8dd 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -659,10 +659,12 @@ static void populate_value(struct refinfo *ref)
 		else if (starts_with(name, "symref"))
 			refname = ref->symref ? ref->symref : "";
 		else if (starts_with(name, "upstream")) {
+			const char *branch_name;
 			/* only local branches may have an upstream */
-			if (!starts_with(ref->refname, "refs/heads/"))
+			if (!skip_prefix(ref->refname, "refs/heads/",
+					 &branch_name))
 				continue;
-			branch = branch_get(ref->refname + 11);
+			branch = branch_get(branch_name);
 
 			refname = branch_get_upstream(branch, NULL);
 			if (!refname)
-- 
2.4.1.528.g00591e3

[PATCH v3 14/14] for-each-ref: accept "%(push)" format

[Jeff King]

Just as we have "%(upstream)" to report the "@{upstream}"
for each ref, this patch adds "%(push)" to match "@{push}".
It supports the same tracking format modifiers as upstream
(because you may want to know, for example, which branches
have commits to push).

Signed-off-by: Jeff King <peff@peff.net>
---
 Documentation/git-for-each-ref.txt |  6 ++++++
 builtin/for-each-ref.c             | 17 +++++++++++++++--
 t/t6300-for-each-ref.sh            | 13 ++++++++++++-
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 4240875..7f8d9a5 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -97,6 +97,12 @@ upstream::
 	or "=" (in sync).  Has no effect if the ref does not have
 	tracking information associated with it.
 
+push::
+	The name of a local ref which represents the `@{push}` location
+	for the displayed ref. Respects `:short`, `:track`, and
+	`:trackshort` options as `upstream` does. Produces an empty
+	string if no `@{push}` ref is configured.
+
 HEAD::
 	'*' if HEAD matches current ref (the checked out branch), ' '
 	otherwise.
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 345d8dd..6847400 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -74,6 +74,7 @@ static struct {
 	{ "contents:body" },
 	{ "contents:signature" },
 	{ "upstream" },
+	{ "push" },
 	{ "symref" },
 	{ "flag" },
 	{ "HEAD" },
@@ -669,6 +670,16 @@ static void populate_value(struct refinfo *ref)
 			refname = branch_get_upstream(branch, NULL);
 			if (!refname)
 				continue;
+		} else if (starts_with(name, "push")) {
+			const char *branch_name;
+			if (!skip_prefix(ref->refname, "refs/heads/",
+					 &branch_name))
+				continue;
+			branch = branch_get(branch_name);
+
+			refname = branch_get_push(branch, NULL);
+			if (!refname)
+				continue;
 		} else if (starts_with(name, "color:")) {
 			char color[COLOR_MAXLEN] = "";
 
@@ -714,7 +725,8 @@ static void populate_value(struct refinfo *ref)
 				refname = shorten_unambiguous_ref(refname,
 						      warn_ambiguous_refs);
 			else if (!strcmp(formatp, "track") &&
-				 starts_with(name, "upstream")) {
+				 (starts_with(name, "upstream") ||
+				  starts_with(name, "push"))) {
 				char buf[40];
 
 				if (stat_tracking_info(branch, &num_ours,
@@ -736,7 +748,8 @@ static void populate_value(struct refinfo *ref)
 				}
 				continue;
 			} else if (!strcmp(formatp, "trackshort") &&
-				   starts_with(name, "upstream")) {
+				   (starts_with(name, "upstream") ||
+				    starts_with(name, "push"))) {
 				assert(branch);
 
 				if (stat_tracking_info(branch, &num_ours,
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index c66bf79..24fc2ba 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -28,7 +28,10 @@ test_expect_success setup '
 	git update-ref refs/remotes/origin/master master &&
 	git remote add origin nowhere &&
 	git config branch.master.remote origin &&
-	git config branch.master.merge refs/heads/master
+	git config branch.master.merge refs/heads/master &&
+	git remote add myfork elsewhere &&
+	git config remote.pushdefault myfork &&
+	git config push.default current
 '
 
 test_atom() {
@@ -47,6 +50,7 @@ test_atom() {
 
 test_atom head refname refs/heads/master
 test_atom head upstream refs/remotes/origin/master
+test_atom head push refs/remotes/myfork/master
 test_atom head objecttype commit
 test_atom head objectsize 171
 test_atom head objectname $(git rev-parse refs/heads/master)
@@ -83,6 +87,7 @@ test_atom head HEAD '*'
 
 test_atom tag refname refs/tags/testtag
 test_atom tag upstream ''
+test_atom tag push ''
 test_atom tag objecttype tag
 test_atom tag objectsize 154
 test_atom tag objectname $(git rev-parse refs/tags/testtag)
@@ -347,6 +352,12 @@ test_expect_success 'Check that :track[short] works when upstream is invalid' '
 	test_cmp expected actual
 '
 
+test_expect_success '%(push) supports tracking specifiers, too' '
+	echo "[ahead 1]" >expected &&
+	git for-each-ref --format="%(push:track)" refs/heads >actual &&
+	test_cmp expected actual
+'
+
 cat >expected <<EOF
 $(git rev-parse --short HEAD)
 EOF
-- 
2.4.1.528.g00591e3

Re: [PATCH v3 0/14] implement @{push} shorthand

[Jeff King]

On Thu, May 21, 2015 at 12:44:29AM -0400, Jeff King wrote:

> This is a re-roll of the series at:
> 
>   http://thread.gmane.org/gmane.comp.version-control.git/268185
> 
> The only changes here are the addition of patches 2 and 6, which are
> both cleanups that help make the other patches more readable/sensible.
> They are the same as what was posted during review of the thread linked
> above.  So there's nothing new here, but of course fresh reviews are
> welcome.

Actually, that's not quite true; I forgot to mention one change:

>   [03/14]: remote.c: drop "remote" pointer from "struct branch"

In this version, this one remembers to also update the API
documentation.

-Peff

Re: [PATCH v3 02/14] remote.c: refactor setup of branch->merge list

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> When we call branch_get() to lookup or create a "struct
> branch", we make sure the "merge" field is filled in so that
> callers can access it. But the conditions under which we do
> so are a little confusing, and can lead to two funny
> situations:
> ...
> In addition to those two fixes, this patch pushes the "do we
> need to setup merge?" logic down into set_merge, where it is
> a bit easier to follow.

Nicely done.  Thanks.

>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
>  remote.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/remote.c b/remote.c
> index bec8b31..ac17e66 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -1636,6 +1636,19 @@ static void set_merge(struct branch *ret)
>  	unsigned char sha1[20];
>  	int i;
>  
> +	if (!ret)
> +		return; /* no branch */
> +	if (ret->merge)
> +		return; /* already run */
> +	if (!ret->remote_name || !ret->merge_nr) {
> +		/*
> +		 * no merge config; let's make sure we don't confuse callers
> +		 * with a non-zero merge_nr but a NULL merge
> +		 */
> +		ret->merge_nr = 0;
> +		return;
> +	}
> +
>  	ret->merge = xcalloc(ret->merge_nr, sizeof(*ret->merge));
>  	for (i = 0; i < ret->merge_nr; i++) {
>  		ret->merge[i] = xcalloc(1, sizeof(**ret->merge));
> @@ -1660,11 +1673,9 @@ struct branch *branch_get(const char *name)
>  		ret = current_branch;
>  	else
>  		ret = make_branch(name, 0);
> -	if (ret && ret->remote_name) {
> +	if (ret && ret->remote_name)
>  		ret->remote = remote_get(ret->remote_name);
> -		if (ret->merge_nr)
> -			set_merge(ret);
> -	}
> +	set_merge(ret);
>  	return ret;
>  }

Re: [PATCH v3 07/14] remote.c: introduce branch_get_upstream helper

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> All of the information needed to find the @{upstream} of a
> branch is included in the branch struct, but callers have to
> navigate a series of possible-NULL values to get there.
> Let's wrap that logic up in an easy-to-read helper.
>
> Signed-off-by: Jeff King <peff@peff.net>

This step in the whole series is a gem.  I cannot believe that we
were content having to repeat that "branch->merge[0]->dst if we can
dereference down to that level" this many times.  Nice clean-up.

> diff --git a/builtin/branch.c b/builtin/branch.c
> index 258fe2f..1eb6215 100644
> --- a/builtin/branch.c
> +++ b/builtin/branch.c
> @@ -123,14 +123,12 @@ static int branch_merged(int kind, const char *name,
>  
>  	if (kind == REF_LOCAL_BRANCH) {
>  		struct branch *branch = branch_get(name);
> +		const char *upstream = branch_get_upstream(branch);
>  		unsigned char sha1[20];
>  
> -		if (branch &&
> -		    branch->merge &&
> -		    branch->merge[0] &&
> -		    branch->merge[0]->dst &&
> +		if (upstream &&
>  		    (reference_name = reference_name_to_free =
> -		     resolve_refdup(branch->merge[0]->dst, RESOLVE_REF_READING,
> +		     resolve_refdup(upstream, RESOLVE_REF_READING,
>  				    sha1, NULL)) != NULL)
>  			reference_rev = lookup_commit_reference(sha1);

Re: [PATCH v3 07/14] remote.c: introduce branch_get_upstream helper

[Jeff King]

On Thu, May 21, 2015 at 11:07:33AM -0700, Junio C Hamano wrote:

> Jeff King <peff@peff.net> writes:
> 
> > All of the information needed to find the @{upstream} of a
> > branch is included in the branch struct, but callers have to
> > navigate a series of possible-NULL values to get there.
> > Let's wrap that logic up in an easy-to-read helper.
> >
> > Signed-off-by: Jeff King <peff@peff.net>
> 
> This step in the whole series is a gem.  I cannot believe that we
> were content having to repeat that "branch->merge[0]->dst if we can
> dereference down to that level" this many times.  Nice clean-up.

There is a related cleanup I resisted, which is that several call-sites
will call stat_tracking_info, then later look directly at
branch->merge[0]->dst without a check for NULL (fill_tracking_info is
such a site).

This works because stat_tracking_info's return value tells us that we
did indeed find an upstream to compare with. But it feels a little leaky
to me. One solution is for stat_tracking_info to pass out the name of
thte upstream, making the caller side something like:

diff --git a/builtin/branch.c b/builtin/branch.c
index cc55ff2..edc4deb 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -425,11 +425,12 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 	int ours, theirs;
 	char *ref = NULL;
 	struct branch *branch = branch_get(branch_name);
+	const char *upstream;
 	struct strbuf fancy = STRBUF_INIT;
 	int upstream_is_gone = 0;
 	int added_decoration = 1;
 
-	switch (stat_tracking_info(branch, &ours, &theirs)) {
+	switch (stat_tracking_info(branch, &ours, &theirs, &upstream)) {
 	case 0:
 		/* no base */
 		return;
@@ -443,7 +444,7 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 	}
 
 	if (show_upstream_ref) {
-		ref = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
+		ref = shorten_unambiguous_ref(upstream, 0);
 		if (want_color(branch_use_color))
 			strbuf_addf(&fancy, "%s%s%s",
 					branch_get_color(BRANCH_COLOR_UPSTREAM),


This is still a little error-prone, though. We assume "upstream" was
filled in depending on the return value of stat_tracking_info. I wonder
if we could get rid of the weird tri-state return value from
stat_tracking_info, and just have callers detect the "there is no base"
case by checking "upstream != NULL".

I dunno. It is not buggy in any of the current callers, so it might not
be worth spending too much time on.

-Peff

Re: [PATCH v3 08/14] remote.c: report specific errors from branch_get_upstream

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> diff --git a/remote.c b/remote.c
> index dca3442..1b7051a 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -1705,10 +1705,35 @@ int branch_merge_matches(struct branch *branch,
>  	return refname_match(branch->merge[i]->src, refname);
>  }
>  
> -const char *branch_get_upstream(struct branch *branch)
> +__attribute((format (printf,2,3)))
> +static const char *error_buf(struct strbuf *err, const char *fmt, ...)
>  {
> -	if (!branch || !branch->merge || !branch->merge[0])
> -		return NULL;
> +	if (err) {
> +		va_list ap;
> +		va_start(ap, fmt);
> +		strbuf_vaddf(err, fmt, ap);
> +		va_end(ap);
> +	}
> +	return NULL;
> +}

Many of our functions return -1 to signal an error, and that is why
it makes sense for our error() helper to return -1 to save code in
the caller, but only because the callers of this private helper use
a NULL to signal an error, this also returns NULL.  If we were to
use the "callers can opt into detailed message by passing strbuf"
pattern more widely, we would want a variant of the above that
returns -1, too.  And such a helper would do the same thing as
above, with only difference from the above is to return -1.

It's a shame that we have to return something from this function,
whose primary purpose is "we may or may not want an error message in
a strbuf, so format the message when and only when we give you a
strbuf", but C forces us to make it "always return NULL to signal an
error to the caller, and optionally format the message into a strbuf
if given".

And the name of this helper function only captures the "optionally
format the message" part, not the "always return NULL" part.

> +const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
> +{
> +	if (!branch)
> +		return error_buf(err, _("HEAD does not point to a branch"));
> +	if (!branch->merge || !branch->merge[0] || !branch->merge[0]->dst) {
> +		if (!ref_exists(branch->refname))
> +			return error_buf(err, _("no such branch: '%s'"),
> +					 branch->name);
> +		if (!branch->merge)
> +			return error_buf(err,
> +					 _("no upstream configured for branch '%s'"),
> +					 branch->name);
> +		return error_buf(err,
> +				 _("upstream branch '%s' not stored as a remote-tracking branch"),
> +				 branch->merge[0]->src);
> +	}
> +
>  	return branch->merge[0]->dst;
>  }

This is a faithful conversion of what the get_upstream_branch() used
to do, but that ref_exists() check and the error checking there look
somewhat out of place.

It makes the reader wonder what should happen when "branch->refname"
does not exist as a ref, but "branch->merge[0]->dst" can be fully
dereferenced.  Should it be an error, or if it is OK, the reason why
it is OK is...?

Re: [PATCH v3 07/14] remote.c: introduce branch_get_upstream helper

[Jeff King]

On Thu, May 21, 2015 at 02:14:29PM -0400, Jeff King wrote:

> There is a related cleanup I resisted, which is that several call-sites
> will call stat_tracking_info, then later look directly at
> branch->merge[0]->dst without a check for NULL (fill_tracking_info is
> such a site).
> 
> This works because stat_tracking_info's return value tells us that we
> did indeed find an upstream to compare with. But it feels a little leaky
> to me. One solution is for stat_tracking_info to pass out the name of
> thte upstream, making the caller side something like:

So just for fun, here is what a whole patch, with the refactoring of the
return value, would look like.

diff --git a/builtin/branch.c b/builtin/branch.c
index cc55ff2..8ecabd1 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -425,25 +425,19 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 	int ours, theirs;
 	char *ref = NULL;
 	struct branch *branch = branch_get(branch_name);
+	const char *upstream;
 	struct strbuf fancy = STRBUF_INIT;
 	int upstream_is_gone = 0;
 	int added_decoration = 1;
 
-	switch (stat_tracking_info(branch, &ours, &theirs)) {
-	case 0:
-		/* no base */
-		return;
-	case -1:
-		/* with "gone" base */
+	if (stat_tracking_info(branch, &ours, &theirs, &upstream) < 0) {
+		if (!upstream)
+			return;
 		upstream_is_gone = 1;
-		break;
-	default:
-		/* with base */
-		break;
 	}
 
 	if (show_upstream_ref) {
-		ref = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
+		ref = shorten_unambiguous_ref(upstream, 0);
 		if (want_color(branch_use_color))
 			strbuf_addf(&fancy, "%s%s%s",
 					branch_get_color(BRANCH_COLOR_UPSTREAM),
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 6847400..05dd23d 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -730,7 +730,7 @@ static void populate_value(struct refinfo *ref)
 				char buf[40];
 
 				if (stat_tracking_info(branch, &num_ours,
-						       &num_theirs) != 1)
+						       &num_theirs, NULL))
 					continue;
 
 				if (!num_ours && !num_theirs)
@@ -753,7 +753,7 @@ static void populate_value(struct refinfo *ref)
 				assert(branch);
 
 				if (stat_tracking_info(branch, &num_ours,
-							&num_theirs) != 1)
+							&num_theirs, NULL))
 					continue;
 
 				if (!num_ours && !num_theirs)
diff --git a/remote.c b/remote.c
index be45a39..6765051 100644
--- a/remote.c
+++ b/remote.c
@@ -2016,12 +2016,15 @@ int ref_newer(const unsigned char *new_sha1, const unsigned char *old_sha1)
 
 /*
  * Compare a branch with its upstream, and save their differences (number
- * of commits) in *num_ours and *num_theirs.
+ * of commits) in *num_ours and *num_theirs. The name of the upstream branch
+ * (or NULL if no upstream is defined) is returned via *upstream_name, if it
+ * is not itself NULL.
  *
- * Return 0 if branch has no upstream (no base), -1 if upstream is missing
- * (with "gone" base), otherwise 1 (with base).
+ * Returns -1 if num_ours and num_theirs could not be filled in (e.g., no
+ * upstream defined, or ref does not exist), 0 otherwise.
  */
-int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
+int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
+		       const char **upstream_name)
 {
 	unsigned char sha1[20];
 	struct commit *ours, *theirs;
@@ -2032,8 +2035,10 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 
 	/* Cannot stat unless we are marked to build on top of somebody else. */
 	base = branch_get_upstream(branch, NULL);
+	if (upstream_name)
+		*upstream_name = base;
 	if (!base)
-		return 0;
+		return -1;
 
 	/* Cannot stat if what we used to build on no longer exists */
 	if (read_ref(base, sha1))
@@ -2051,7 +2056,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	/* are we the same? */
 	if (theirs == ours) {
 		*num_theirs = *num_ours = 0;
-		return 1;
+		return 0;
 	}
 
 	/* Run "rev-list --left-right ours...theirs" internally... */
@@ -2087,7 +2092,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	/* clear object flags smudged by the above traversal */
 	clear_commit_marks(ours, ALL_REV_FLAGS);
 	clear_commit_marks(theirs, ALL_REV_FLAGS);
-	return 1;
+	return 0;
 }
 
 /*
@@ -2096,23 +2101,17 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 int format_tracking_info(struct branch *branch, struct strbuf *sb)
 {
 	int ours, theirs;
+	const char *full_base;
 	char *base;
 	int upstream_is_gone = 0;
 
-	switch (stat_tracking_info(branch, &ours, &theirs)) {
-	case 0:
-		/* no base */
-		return 0;
-	case -1:
-		/* with "gone" base */
+	if (stat_tracking_info(branch, &ours, &theirs, &full_base) < 0) {
+		if (!full_base)
+			return 0;
 		upstream_is_gone = 1;
-		break;
-	default:
-		/* with base */
-		break;
 	}
 
-	base = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
+	base = shorten_unambiguous_ref(full_base, 0);
 	if (upstream_is_gone) {
 		strbuf_addf(sb,
 			_("Your branch is based on '%s', but the upstream is gone.\n"),
diff --git a/remote.h b/remote.h
index 3326f2b..312b7ca 100644
--- a/remote.h
+++ b/remote.h
@@ -249,7 +249,8 @@ enum match_refs_flags {
 };
 
 /* Reporting of tracking info */
-int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs);
+int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
+		       const char **upstream_name);
 int format_tracking_info(struct branch *branch, struct strbuf *sb);
 
 struct ref *get_local_heads(void);
diff --git a/wt-status.c b/wt-status.c
index 38cb165..7c8ae57 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -1532,21 +1532,15 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
 
 	color_fprintf(s->fp, branch_color_local, "%s", branch_name);
 
-	switch (stat_tracking_info(branch, &num_ours, &num_theirs)) {
-	case 0:
-		/* no base */
-		fputc(s->null_termination ? '\0' : '\n', s->fp);
-		return;
-	case -1:
-		/* with "gone" base */
+	if (stat_tracking_info(branch, &num_ours, &num_theirs, &base) < 0) {
+		if (!base) {
+			fputc(s->null_termination ? '\0' : '\n', s->fp);
+			return;
+		}
+
 		upstream_is_gone = 1;
-		break;
-	default:
-		/* with base */
-		break;
 	}
 
-	base = branch->merge[0]->dst;
 	base = shorten_unambiguous_ref(base, 0);
 	color_fprintf(s->fp, header_color, "...");
 	color_fprintf(s->fp, branch_color_remote, "%s", base);

Re: [PATCH v3 0/14] implement @{push} shorthand

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> On Thu, May 21, 2015 at 12:44:29AM -0400, Jeff King wrote:
>
>> This is a re-roll of the series at:
>> 
>>   http://thread.gmane.org/gmane.comp.version-control.git/268185
>> 
>> The only changes here are the addition of patches 2 and 6, which are
>> both cleanups that help make the other patches more readable/sensible.
>> They are the same as what was posted during review of the thread linked
>> above.  So there's nothing new here, but of course fresh reviews are
>> welcome.
>
> Actually, that's not quite true; I forgot to mention one change:
>
>>   [03/14]: remote.c: drop "remote" pointer from "struct branch"
>
> In this version, this one remembers to also update the API
> documentation.
>
> -Peff

Thanks for a pleasant read.
Will queue.

Re: [PATCH v3 08/14] remote.c: report specific errors from branch_get_upstream

[Jeff King]

On Thu, May 21, 2015 at 11:33:58AM -0700, Junio C Hamano wrote:

> > +static const char *error_buf(struct strbuf *err, const char *fmt, ...)
> >  {
> > -	if (!branch || !branch->merge || !branch->merge[0])
> > -		return NULL;
> > +	if (err) {
> > +		va_list ap;
> > +		va_start(ap, fmt);
> > +		strbuf_vaddf(err, fmt, ap);
> > +		va_end(ap);
> > +	}
> > +	return NULL;
> > +}
> 
> Many of our functions return -1 to signal an error, and that is why
> it makes sense for our error() helper to return -1 to save code in
> the caller, but only because the callers of this private helper use
> a NULL to signal an error, this also returns NULL.  If we were to
> use the "callers can opt into detailed message by passing strbuf"
> pattern more widely, we would want a variant of the above that
> returns -1, too.  And such a helper would do the same thing as
> above, with only difference from the above is to return -1.

Yeah, this is not really a good general-purpose purpose function in that
sense. I have often wanted an error() that returns NULL, but avoided
adding just because it seemed like needless proliferation.

The real reason to include the return value at all in error() is to let
you turn two-liners into one-liners. We could drop the return value from
this helper entirely (or make it -1, but of course no callers would use
it) and write it out long-hand in the callers:

  if (!branch->merge) {
	error_buf(err, ...);
	return NULL;
  }

That is really not so bad, as there are only a handful of callers.

> > +const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
> > +{
> > +	if (!branch)
> > +		return error_buf(err, _("HEAD does not point to a branch"));
> > +	if (!branch->merge || !branch->merge[0] || !branch->merge[0]->dst) {
> > +		if (!ref_exists(branch->refname))
> > +			return error_buf(err, _("no such branch: '%s'"),
> > +					 branch->name);
> > +		if (!branch->merge)
> > +			return error_buf(err,
> > +					 _("no upstream configured for branch '%s'"),
> > +					 branch->name);
> > +		return error_buf(err,
> > +				 _("upstream branch '%s' not stored as a remote-tracking branch"),
> > +				 branch->merge[0]->src);
> > +	}
> > +
> >  	return branch->merge[0]->dst;
> >  }
> 
> This is a faithful conversion of what the get_upstream_branch() used
> to do, but that ref_exists() check and the error checking there look
> somewhat out of place.
> 
> It makes the reader wonder what should happen when "branch->refname"
> does not exist as a ref, but "branch->merge[0]->dst" can be fully
> dereferenced.  Should it be an error, or if it is OK, the reason why
> it is OK is...?

Yeah, my goal here was to faithfully keep the same logic, but I had a
similar head-scratching moment. What would make more sense to me is:

  if (!branch)
	return error("HEAD does not point to a branch");

  if (!branch->merge || !branch->merge[0]) {
	/*
	 * no merge config; is it because the user didn't define any, or
	 * because it is not a real branch, and get_branch auto-vivified
	 * it?
	 */
	if (!ref_exists(branch->refname))
		return error("no such branch");
	return error("no upstream configured for branch");
  }

  if (!branch->merge[0]->dst)
	return error("upstream branch not stored as a remote-tracking branch");

  return branch->merge[0]->dst;


Hopefully the comment there answers your question; it is not that we
truly care whether the ref exists, but only that we are trying to tell
the difference between a "real" branch and a struct that is an artifact
of our internal code.

Note also that the original may dereference branch->merge[0] even if it
is NULL. I think that can't actually happen in practice (we only
allocate branch->merge if we have at least one item to put in it, and
all of the checks of branch->merge[0] are actually being over-careful).
But the code I just wrote above does not have that problem.

-Peff

Re: [PATCH v3 07/14] remote.c: introduce branch_get_upstream helper

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> On Thu, May 21, 2015 at 02:14:29PM -0400, Jeff King wrote:
>
>> There is a related cleanup I resisted, which is that several call-sites
>> will call stat_tracking_info, then later look directly at
>> branch->merge[0]->dst without a check for NULL (fill_tracking_info is
>> such a site).
>> 
>> This works because stat_tracking_info's return value tells us that we
>> did indeed find an upstream to compare with. But it feels a little leaky
>> to me. One solution is for stat_tracking_info to pass out the name of
>> thte upstream, making the caller side something like:
>
> So just for fun, here is what a whole patch, with the refactoring of the
> return value, would look like.

It looks much nicer and reads better, at least to me.

Nice.

> diff --git a/builtin/branch.c b/builtin/branch.c
> index cc55ff2..8ecabd1 100644
> --- a/builtin/branch.c
> +++ b/builtin/branch.c
> @@ -425,25 +425,19 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
>  	int ours, theirs;
>  	char *ref = NULL;
>  	struct branch *branch = branch_get(branch_name);
> +	const char *upstream;
>  	struct strbuf fancy = STRBUF_INIT;
>  	int upstream_is_gone = 0;
>  	int added_decoration = 1;
>  
> -	switch (stat_tracking_info(branch, &ours, &theirs)) {
> -	case 0:
> -		/* no base */
> -		return;
> -	case -1:
> -		/* with "gone" base */
> +	if (stat_tracking_info(branch, &ours, &theirs, &upstream) < 0) {
> +		if (!upstream)
> +			return;
>  		upstream_is_gone = 1;
> -		break;
> -	default:
> -		/* with base */
> -		break;
>  	}
>  
>  	if (show_upstream_ref) {
> -		ref = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
> +		ref = shorten_unambiguous_ref(upstream, 0);
>  		if (want_color(branch_use_color))
>  			strbuf_addf(&fancy, "%s%s%s",
>  					branch_get_color(BRANCH_COLOR_UPSTREAM),
> diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
> index 6847400..05dd23d 100644
> --- a/builtin/for-each-ref.c
> +++ b/builtin/for-each-ref.c
> @@ -730,7 +730,7 @@ static void populate_value(struct refinfo *ref)
>  				char buf[40];
>  
>  				if (stat_tracking_info(branch, &num_ours,
> -						       &num_theirs) != 1)
> +						       &num_theirs, NULL))
>  					continue;
>  
>  				if (!num_ours && !num_theirs)
> @@ -753,7 +753,7 @@ static void populate_value(struct refinfo *ref)
>  				assert(branch);
>  
>  				if (stat_tracking_info(branch, &num_ours,
> -							&num_theirs) != 1)
> +							&num_theirs, NULL))
>  					continue;
>  
>  				if (!num_ours && !num_theirs)
> diff --git a/remote.c b/remote.c
> index be45a39..6765051 100644
> --- a/remote.c
> +++ b/remote.c
> @@ -2016,12 +2016,15 @@ int ref_newer(const unsigned char *new_sha1, const unsigned char *old_sha1)
>  
>  /*
>   * Compare a branch with its upstream, and save their differences (number
> - * of commits) in *num_ours and *num_theirs.
> + * of commits) in *num_ours and *num_theirs. The name of the upstream branch
> + * (or NULL if no upstream is defined) is returned via *upstream_name, if it
> + * is not itself NULL.
>   *
> - * Return 0 if branch has no upstream (no base), -1 if upstream is missing
> - * (with "gone" base), otherwise 1 (with base).
> + * Returns -1 if num_ours and num_theirs could not be filled in (e.g., no
> + * upstream defined, or ref does not exist), 0 otherwise.
>   */
> -int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
> +int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
> +		       const char **upstream_name)
>  {
>  	unsigned char sha1[20];
>  	struct commit *ours, *theirs;
> @@ -2032,8 +2035,10 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
>  
>  	/* Cannot stat unless we are marked to build on top of somebody else. */
>  	base = branch_get_upstream(branch, NULL);
> +	if (upstream_name)
> +		*upstream_name = base;
>  	if (!base)
> -		return 0;
> +		return -1;
>  
>  	/* Cannot stat if what we used to build on no longer exists */
>  	if (read_ref(base, sha1))
> @@ -2051,7 +2056,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
>  	/* are we the same? */
>  	if (theirs == ours) {
>  		*num_theirs = *num_ours = 0;
> -		return 1;
> +		return 0;
>  	}
>  
>  	/* Run "rev-list --left-right ours...theirs" internally... */
> @@ -2087,7 +2092,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
>  	/* clear object flags smudged by the above traversal */
>  	clear_commit_marks(ours, ALL_REV_FLAGS);
>  	clear_commit_marks(theirs, ALL_REV_FLAGS);
> -	return 1;
> +	return 0;
>  }
>  
>  /*
> @@ -2096,23 +2101,17 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
>  int format_tracking_info(struct branch *branch, struct strbuf *sb)
>  {
>  	int ours, theirs;
> +	const char *full_base;
>  	char *base;
>  	int upstream_is_gone = 0;
>  
> -	switch (stat_tracking_info(branch, &ours, &theirs)) {
> -	case 0:
> -		/* no base */
> -		return 0;
> -	case -1:
> -		/* with "gone" base */
> +	if (stat_tracking_info(branch, &ours, &theirs, &full_base) < 0) {
> +		if (!full_base)
> +			return 0;
>  		upstream_is_gone = 1;
> -		break;
> -	default:
> -		/* with base */
> -		break;
>  	}
>  
> -	base = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
> +	base = shorten_unambiguous_ref(full_base, 0);
>  	if (upstream_is_gone) {
>  		strbuf_addf(sb,
>  			_("Your branch is based on '%s', but the upstream is gone.\n"),
> diff --git a/remote.h b/remote.h
> index 3326f2b..312b7ca 100644
> --- a/remote.h
> +++ b/remote.h
> @@ -249,7 +249,8 @@ enum match_refs_flags {
>  };
>  
>  /* Reporting of tracking info */
> -int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs);
> +int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
> +		       const char **upstream_name);
>  int format_tracking_info(struct branch *branch, struct strbuf *sb);
>  
>  struct ref *get_local_heads(void);
> diff --git a/wt-status.c b/wt-status.c
> index 38cb165..7c8ae57 100644
> --- a/wt-status.c
> +++ b/wt-status.c
> @@ -1532,21 +1532,15 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
>  
>  	color_fprintf(s->fp, branch_color_local, "%s", branch_name);
>  
> -	switch (stat_tracking_info(branch, &num_ours, &num_theirs)) {
> -	case 0:
> -		/* no base */
> -		fputc(s->null_termination ? '\0' : '\n', s->fp);
> -		return;
> -	case -1:
> -		/* with "gone" base */
> +	if (stat_tracking_info(branch, &num_ours, &num_theirs, &base) < 0) {
> +		if (!base) {
> +			fputc(s->null_termination ? '\0' : '\n', s->fp);
> +			return;
> +		}
> +
>  		upstream_is_gone = 1;
> -		break;
> -	default:
> -		/* with base */
> -		break;
>  	}
>  
> -	base = branch->merge[0]->dst;
>  	base = shorten_unambiguous_ref(base, 0);
>  	color_fprintf(s->fp, header_color, "...");
>  	color_fprintf(s->fp, branch_color_remote, "%s", base);

Re: [PATCH v3 08/14] remote.c: report specific errors from branch_get_upstream

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> On Thu, May 21, 2015 at 11:33:58AM -0700, Junio C Hamano wrote:
>
>> > +static const char *error_buf(struct strbuf *err, const char *fmt, ...)
>> >  {
>> > -	if (!branch || !branch->merge || !branch->merge[0])
>> > -		return NULL;
>> > +	if (err) {
>> > +		va_list ap;
>> > +		va_start(ap, fmt);
>> > +		strbuf_vaddf(err, fmt, ap);
>> > +		va_end(ap);
>> > +	}
>> > +	return NULL;
>> > +}
>> 
>> Many of our functions return -1 to signal an error, and that is why
>> it makes sense for our error() helper to return -1 to save code in
>> the caller, but only because the callers of this private helper use
>> a NULL to signal an error, this also returns NULL.  If we were to
>> use the "callers can opt into detailed message by passing strbuf"
>> pattern more widely, we would want a variant of the above that
>> returns -1, too.  And such a helper would do the same thing as
>> above, with only difference from the above is to return -1.
>
> Yeah, this is not really a good general-purpose purpose function in that
> sense. I have often wanted an error() that returns NULL, but avoided
> adding just because it seemed like needless proliferation.
>
> The real reason to include the return value at all in error() is to let
> you turn two-liners into one-liners.

Yeah, our error() returns -1 to save code in the caller.  And the
callers of this private helper all want to return NULL, so this
returns NULL for the same reason.

> We could drop the return value from
> this helper entirely (or make it -1, but of course no callers would use
> it) and write it out long-hand in the callers:
>
>   if (!branch->merge) {
> 	error_buf(err, ...);
> 	return NULL;
>   }
>
> That is really not so bad, as there are only a handful of callers.

That may happen when somebody (perhaps Jonathan?) wants to push the
"let's optionally pass strbuf to format messages into" approach
forward, and most likely be done by adding a similar function to
usage.c next to error_builtin() and friends.  As long as we do not
forget to reimplement this helper in terms of that public function
when it happens, what we have right now after this patch would be
fine.

> Yeah, my goal here was to faithfully keep the same logic, but I had a
> similar head-scratching moment. What would make more sense to me is:
>
>   if (!branch)
> 	return error("HEAD does not point to a branch");
>
>   if (!branch->merge || !branch->merge[0]) {
> 	/*
> 	 * no merge config; is it because the user didn't define any, or
> 	 * because it is not a real branch, and get_branch auto-vivified
> 	 * it?
> 	 */
> 	if (!ref_exists(branch->refname))
> 		return error("no such branch");
> 	return error("no upstream configured for branch");
>   }
>
>   if (!branch->merge[0]->dst)
> 	return error("upstream branch not stored as a remote-tracking branch");
>
>   return branch->merge[0]->dst;
>
> Hopefully the comment there answers your question; it is not that we
> truly care whether the ref exists, but only that we are trying to tell
> the difference between a "real" branch and a struct that is an artifact
> of our internal code.

Well, answering "my" question here on the list wouldn't help future
readers of the code very much ;-)

> Note also that the original may dereference branch->merge[0] even if it
> is NULL. I think that can't actually happen in practice (we only
> allocate branch->merge if we have at least one item to put in it, and
> all of the checks of branch->merge[0] are actually being over-careful).
> But the code I just wrote above does not have that problem.

Perhaps update the patch with this explanation in the log message,
as a separate preparatory step?

Thanks.

Re: [PATCH v3 08/14] remote.c: report specific errors from branch_get_upstream

[Jeff King]

On Thu, May 21, 2015 at 12:25:57PM -0700, Junio C Hamano wrote:

> > Note also that the original may dereference branch->merge[0] even if it
> > is NULL. I think that can't actually happen in practice (we only
> > allocate branch->merge if we have at least one item to put in it, and
> > all of the checks of branch->merge[0] are actually being over-careful).
> > But the code I just wrote above does not have that problem.
> 
> Perhaps update the patch with this explanation in the log message,
> as a separate preparatory step?

I decided on a separate patch on top which improves the logic and
explains the issues. Here it is (it goes on top of the existing patch 8,
"report specific errors from branch_get_upstream").

-- >8 --
Subject: remote.c: untangle error logic in branch_get_upstream

The error-diagnosis logic in branch_get_upstream was copied
straight from sha1_name.c in the previous commit. However,
because we check all error cases and upfront and then later
diagnose them, the logic is a bit tangled. In particular:

  - if branch->merge[0] is NULL, we may end up dereferencing
    it for an error message (in practice, it should never be
    NULL, so this is probably not a triggerable bug).

  - We may enter the code path because branch->merge[0]->dst
    is NULL, but we then start our error diagnosis by
    checking whether our local branch exists. But that is
    only relevant to diagnosing missing merge config, not a
    missing tracking ref; our diagnosis may hide the real
    problem.

Instead, let's just use a sequence of "if" blocks to check
for each error type, diagnose it, and return NULL.

Signed-off-by: Jeff King <peff@peff.net>
---
 remote.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/remote.c b/remote.c
index 1b7051a..d2519c2 100644
--- a/remote.c
+++ b/remote.c
@@ -1721,18 +1721,25 @@ const char *branch_get_upstream(struct branch *branch, struct strbuf *err)
 {
 	if (!branch)
 		return error_buf(err, _("HEAD does not point to a branch"));
-	if (!branch->merge || !branch->merge[0] || !branch->merge[0]->dst) {
+
+	if (!branch->merge || !branch->merge[0]) {
+		/*
+		 * no merge config; is it because the user didn't define any,
+		 * or because it is not a real branch, and get_branch
+		 * auto-vivified it?
+		 */
 		if (!ref_exists(branch->refname))
 			return error_buf(err, _("no such branch: '%s'"),
 					 branch->name);
-		if (!branch->merge)
-			return error_buf(err,
-					 _("no upstream configured for branch '%s'"),
-					 branch->name);
+		return error_buf(err,
+				 _("no upstream configured for branch '%s'"),
+				 branch->name);
+	}
+
+	if (!branch->merge[0]->dst)
 		return error_buf(err,
 				 _("upstream branch '%s' not stored as a remote-tracking branch"),
 				 branch->merge[0]->src);
-	}
 
 	return branch->merge[0]->dst;
 }
-- 
2.4.1.528.g00591e3

Re: [PATCH v3 08/14] remote.c: report specific errors from branch_get_upstream

[Jeff King]

On Thu, May 21, 2015 at 08:46:43PM -0400, Jeff King wrote:

> On Thu, May 21, 2015 at 12:25:57PM -0700, Junio C Hamano wrote:
> 
> > > Note also that the original may dereference branch->merge[0] even if it
> > > is NULL. I think that can't actually happen in practice (we only
> > > allocate branch->merge if we have at least one item to put in it, and
> > > all of the checks of branch->merge[0] are actually being over-careful).
> > > But the code I just wrote above does not have that problem.
> > 
> > Perhaps update the patch with this explanation in the log message,
> > as a separate preparatory step?
> 
> I decided on a separate patch on top which improves the logic and
> explains the issues. Here it is (it goes on top of the existing patch 8,
> "report specific errors from branch_get_upstream").
> 
> -- >8 --
> Subject: remote.c: untangle error logic in branch_get_upstream

And then on top of that, we can add in this cleanup I showed earlier.

Both of these should insert into the series without any trouble, but let
me know if you run into problems and I can repost the whole thing.

-- >8 --
Subject: remote.c: return upstream name from stat_tracking_info

After calling stat_tracking_info, callers often want to
print the name of the upstream branch (in addition to the
tracking count). To do this, they have to access
branch->merge->dst[0] themselves. This is not wrong, as the
return value from stat_tracking_info tells us whether we
have an upstream branch or not. But it is a bit leaky, as we
make an assumption about how it calculated the upstream
name.

Instead, let's add an out-parameter that lets the caller
know the upstream name we found.

As a bonus, we can get rid of the unusual tri-state return
from the function. We no longer need to use it to
differentiate between "no tracking config" and "tracking ref
does not exist" (since you can check the upstream_name for
that), so we can just use the usual 0/-1 convention for
success/error.

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/branch.c       | 16 +++++-----------
 builtin/for-each-ref.c |  4 ++--
 remote.c               | 35 +++++++++++++++++------------------
 remote.h               |  3 ++-
 wt-status.c            | 18 ++++++------------
 5 files changed, 32 insertions(+), 44 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index cc55ff2..8ecabd1 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -425,25 +425,19 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 	int ours, theirs;
 	char *ref = NULL;
 	struct branch *branch = branch_get(branch_name);
+	const char *upstream;
 	struct strbuf fancy = STRBUF_INIT;
 	int upstream_is_gone = 0;
 	int added_decoration = 1;
 
-	switch (stat_tracking_info(branch, &ours, &theirs)) {
-	case 0:
-		/* no base */
-		return;
-	case -1:
-		/* with "gone" base */
+	if (stat_tracking_info(branch, &ours, &theirs, &upstream) < 0) {
+		if (!upstream)
+			return;
 		upstream_is_gone = 1;
-		break;
-	default:
-		/* with base */
-		break;
 	}
 
 	if (show_upstream_ref) {
-		ref = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
+		ref = shorten_unambiguous_ref(upstream, 0);
 		if (want_color(branch_use_color))
 			strbuf_addf(&fancy, "%s%s%s",
 					branch_get_color(BRANCH_COLOR_UPSTREAM),
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 18d209b..92bd2b2 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -716,7 +716,7 @@ static void populate_value(struct refinfo *ref)
 				char buf[40];
 
 				if (stat_tracking_info(branch, &num_ours,
-						       &num_theirs) != 1)
+						       &num_theirs, NULL))
 					continue;
 
 				if (!num_ours && !num_theirs)
@@ -738,7 +738,7 @@ static void populate_value(struct refinfo *ref)
 				assert(branch);
 
 				if (stat_tracking_info(branch, &num_ours,
-							&num_theirs) != 1)
+							&num_theirs, NULL))
 					continue;
 
 				if (!num_ours && !num_theirs)
diff --git a/remote.c b/remote.c
index d2519c2..c884574 100644
--- a/remote.c
+++ b/remote.c
@@ -1938,12 +1938,15 @@ int ref_newer(const unsigned char *new_sha1, const unsigned char *old_sha1)
 
 /*
  * Compare a branch with its upstream, and save their differences (number
- * of commits) in *num_ours and *num_theirs.
+ * of commits) in *num_ours and *num_theirs. The name of the upstream branch
+ * (or NULL if no upstream is defined) is returned via *upstream_name, if it
+ * is not itself NULL.
  *
- * Return 0 if branch has no upstream (no base), -1 if upstream is missing
- * (with "gone" base), otherwise 1 (with base).
+ * Returns -1 if num_ours and num_theirs could not be filled in (e.g., no
+ * upstream defined, or ref does not exist), 0 otherwise.
  */
-int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
+int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
+		       const char **upstream_name)
 {
 	unsigned char sha1[20];
 	struct commit *ours, *theirs;
@@ -1954,8 +1957,10 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 
 	/* Cannot stat unless we are marked to build on top of somebody else. */
 	base = branch_get_upstream(branch, NULL);
+	if (upstream_name)
+		*upstream_name = base;
 	if (!base)
-		return 0;
+		return -1;
 
 	/* Cannot stat if what we used to build on no longer exists */
 	if (read_ref(base, sha1))
@@ -1973,7 +1978,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	/* are we the same? */
 	if (theirs == ours) {
 		*num_theirs = *num_ours = 0;
-		return 1;
+		return 0;
 	}
 
 	/* Run "rev-list --left-right ours...theirs" internally... */
@@ -2009,7 +2014,7 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	/* clear object flags smudged by the above traversal */
 	clear_commit_marks(ours, ALL_REV_FLAGS);
 	clear_commit_marks(theirs, ALL_REV_FLAGS);
-	return 1;
+	return 0;
 }
 
 /*
@@ -2018,23 +2023,17 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 int format_tracking_info(struct branch *branch, struct strbuf *sb)
 {
 	int ours, theirs;
+	const char *full_base;
 	char *base;
 	int upstream_is_gone = 0;
 
-	switch (stat_tracking_info(branch, &ours, &theirs)) {
-	case 0:
-		/* no base */
-		return 0;
-	case -1:
-		/* with "gone" base */
+	if (stat_tracking_info(branch, &ours, &theirs, &full_base) < 0) {
+		if (!full_base)
+			return 0;
 		upstream_is_gone = 1;
-		break;
-	default:
-		/* with base */
-		break;
 	}
 
-	base = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
+	base = shorten_unambiguous_ref(full_base, 0);
 	if (upstream_is_gone) {
 		strbuf_addf(sb,
 			_("Your branch is based on '%s', but the upstream is gone.\n"),
diff --git a/remote.h b/remote.h
index 03ca005..357a909 100644
--- a/remote.h
+++ b/remote.h
@@ -239,7 +239,8 @@ enum match_refs_flags {
 };
 
 /* Reporting of tracking info */
-int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs);
+int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs,
+		       const char **upstream_name);
 int format_tracking_info(struct branch *branch, struct strbuf *sb);
 
 struct ref *get_local_heads(void);
diff --git a/wt-status.c b/wt-status.c
index 38cb165..7c8ae57 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -1532,21 +1532,15 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
 
 	color_fprintf(s->fp, branch_color_local, "%s", branch_name);
 
-	switch (stat_tracking_info(branch, &num_ours, &num_theirs)) {
-	case 0:
-		/* no base */
-		fputc(s->null_termination ? '\0' : '\n', s->fp);
-		return;
-	case -1:
-		/* with "gone" base */
+	if (stat_tracking_info(branch, &num_ours, &num_theirs, &base) < 0) {
+		if (!base) {
+			fputc(s->null_termination ? '\0' : '\n', s->fp);
+			return;
+		}
+
 		upstream_is_gone = 1;
-		break;
-	default:
-		/* with base */
-		break;
 	}
 
-	base = branch->merge[0]->dst;
 	base = shorten_unambiguous_ref(base, 0);
 	color_fprintf(s->fp, header_color, "...");
 	color_fprintf(s->fp, branch_color_remote, "%s", base);
-- 
2.4.1.528.g00591e3