[PATCH 1/3] merge: new autosetupmerge option 'simple' for matching branches

["Tao Klerks via GitGitGadget" <gitgitgadget@gmail.com>]

From: Tao Klerks <tao@klerks.biz>

The push.defaut option "simple" helps produce
predictable/understandable behavior for beginners,
where they don't accidentally push to the
"wrong" branch in centralized workflows. If they
create a local branch with a different name
and then try to do a plain push, it will
helpfully fail and explain why.

However, such users can often find themselves
confused by the behavior of git after they first
branch, and before they push. At that stage,
their upstream tracking branch is the original
remote branch, and pull (for example) behaves
very differently to how it later does when they
create their own same-name remote branch.

This commit introduces a new option to the
branch.autosetupmerge setting, "simple",
which is intended to be consistent with and
complementary to the push.default "simple"
option.

It will set up automatic tracking for a new
branch only if the remote ref is a branch and
that remote branch name matches the new local
branch name. It is a reduction in scope of
the existing default option, "true".

Signed-off-by: Tao Klerks <tao@klerks.biz>
---
 branch.c | 9 +++++++++
 branch.h | 1 +
 config.c | 3 +++
 3 files changed, 13 insertions(+)

diff --git a/branch.c b/branch.c
index 6b31df539a5..246bc82ce3c 100644
--- a/branch.c
+++ b/branch.c
@@ -256,6 +256,15 @@ static void setup_tracking(const char *new_ref, const char *orig_ref,
 		die(_("not tracking: ambiguous information for ref %s"),
 		    orig_ref);
 
+	if (track == BRANCH_TRACK_SIMPLE) {
+		// only track if remote branch name matches
+		// (tracking.srcs must contain only one entry from find_tracked_branch with this config)
+		if (strncmp(tracking.srcs->items[0].string, "refs/heads/", 11))
+			return;
+		if (strcmp(tracking.srcs->items[0].string + 11, new_ref))
+			return;
+	}
+
 	if (tracking.srcs->nr < 1)
 		string_list_append(tracking.srcs, orig_ref);
 	if (install_branch_config_multiple_remotes(config_flags, new_ref,
diff --git a/branch.h b/branch.h
index 04df2aa5b51..560b6b96a8f 100644
--- a/branch.h
+++ b/branch.h
@@ -12,6 +12,7 @@ enum branch_track {
 	BRANCH_TRACK_EXPLICIT,
 	BRANCH_TRACK_OVERRIDE,
 	BRANCH_TRACK_INHERIT,
+	BRANCH_TRACK_SIMPLE,
 };
 
 extern enum branch_track git_branch_track;
diff --git a/config.c b/config.c
index e0c03d154c9..cc586ac816c 100644
--- a/config.c
+++ b/config.c
@@ -1673,6 +1673,9 @@ static int git_default_branch_config(const char *var, const char *value)
 		} else if (value && !strcmp(value, "inherit")) {
 			git_branch_track = BRANCH_TRACK_INHERIT;
 			return 0;
+		} else if (value && !strcmp(value, "simple")) {
+			git_branch_track = BRANCH_TRACK_SIMPLE;
+			return 0;
 		}
 		git_branch_track = git_config_bool(var, value);
 		return 0;
-- 
gitgitgadget