[PATCH v3 19/19] refs.c: pass **transaction to commit and have it clear the pointer

[Ronnie Sahlberg <sahlberg@google.com>]

Change ref_transaction_commit to take a pointer to a pointer for the
transaction. This allows us to clear the transaction pointer from within
ref_transaction_commit so that it becomes NULL in the caller.

This makes transaction handling in the callers much nicer since instead of
having to write horrible code like :
	t = ref_transaction_begin();
	if ((!t ||
	    ref_transaction_update(t, refname, sha1, oldval, flags,
				   !!oldval)) ||
	    (ref_transaction_commit(t, action, &err) && !(t = NULL))) {
		ref_transaction_rollback(t);

we can now just do the much nicer
	t = ref_transaction_begin();
	if (!t ||
	    ref_transaction_update(t, refname, sha1, oldval, flags,
				   !!oldval) ||
	    ref_transaction_commit(&t, action, &err)) {
		ref_transaction_rollback(t);

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 branch.c             |  4 ++--
 builtin/commit.c     |  2 +-
 builtin/replace.c    |  2 +-
 builtin/tag.c        |  2 +-
 builtin/update-ref.c |  2 +-
 fast-import.c        |  7 +++----
 refs.c               | 18 ++++++++++--------
 refs.h               |  3 ++-
 sequencer.c          |  7 +++----
 9 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/branch.c b/branch.c
index 23cde1e..5d68467 100644
--- a/branch.c
+++ b/branch.c
@@ -303,14 +303,14 @@ void create_branch(const char *head,
 			if (!transaction ||
 			    ref_transaction_update(transaction, ref.buf, sha1,
 						   NULL, 0, 0) ||
-			    ref_transaction_commit(transaction, msg, &err))
+			    ref_transaction_commit(&transaction, msg, &err))
 			  die_errno(_("%s: failed to write ref: %s"),
 				    ref.buf, err);
 		} else {
 			if (!transaction ||
 			    ref_transaction_create(transaction, ref.buf, sha1,
 						   0) ||
-			    ref_transaction_commit(transaction, msg, &err))
+			    ref_transaction_commit(&transaction, msg, &err))
 			  die_errno(_("%s: failed to write ref: %s"),
 				    ref.buf, err);
 		}
diff --git a/builtin/commit.c b/builtin/commit.c
index 7e4c306..3142827 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1682,7 +1682,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 				   current_head ? 
 				   current_head->object.sha1 : NULL,
 				   0, !!current_head) ||
-	    ref_transaction_commit(transaction, sb.buf, &err)) {
+	    ref_transaction_commit(&transaction, sb.buf, &err)) {
 		rollback_index_files();
 		die(_("HEAD: cannot update ref: %s"), err);
 	}
diff --git a/builtin/replace.c b/builtin/replace.c
index cf0f56d..51e9ddf 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c
@@ -162,7 +162,7 @@ static int replace_object(const char *object_ref, const char *replace_ref,
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref, repl, prev,
 				   0, !is_null_sha1(prev)) ||
-	    ref_transaction_commit(transaction, NULL, &err))
+	    ref_transaction_commit(&transaction, NULL, &err))
 	  die(_("%s: failed to replace ref: %s"), ref, err);
 
 	return 0;
diff --git a/builtin/tag.c b/builtin/tag.c
index dd53fb4..60b57a1 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -646,7 +646,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	if (!transaction ||
 	    ref_transaction_update(transaction, ref.buf, object, prev,
 				   0, !is_null_sha1(prev)) ||
-	    ref_transaction_commit(transaction, NULL, &err))
+	    ref_transaction_commit(&transaction, NULL, &err))
 	  die(_("%s: cannot update the ref: %s"), ref.buf, err);
 	if (force && !is_null_sha1(prev) && hashcmp(prev, object))
 		printf(_("Updated tag '%s' (was %s)\n"), tag, find_unique_abbrev(prev, DEFAULT_ABBREV));
diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index a600ab3..4a0901d 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -373,7 +373,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		if (end_null)
 			line_termination = '\0';
 		update_refs_stdin();
-		if (ref_transaction_commit(transaction, msg, &err))
+		if (ref_transaction_commit(&transaction, msg, &err))
 			die("update_ref failed: %s", err);
 		return 0;
 	}
diff --git a/fast-import.c b/fast-import.c
index a2b05fa..3ce2f47 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -1703,11 +1703,10 @@ static int update_branch(struct branch *b)
 		}
 	}
 	transaction = ref_transaction_begin();
-	if ((!transaction ||
+	if (!transaction ||
 	    ref_transaction_update(transaction, b->name, b->sha1, old_sha1,
-				   0, 1)) ||
-	    (ref_transaction_commit(transaction, msg, &err) &&
-	     !(transaction = NULL))) {
+				   0, 1) ||
+	    ref_transaction_commit(&transaction, msg, &err)) {
 		ref_transaction_rollback(transaction);
 		return error("Unable to update branch %s: %s", b->name, err);
 	}
diff --git a/refs.c b/refs.c
index ffa9c83..0b60250 100644
--- a/refs.c
+++ b/refs.c
@@ -3401,10 +3401,10 @@ int update_ref(const char *action, const char *refname,
 	char *err = NULL;
 
 	t = ref_transaction_begin();
-	if ((!t ||
+	if (!t ||
 	    ref_transaction_update(t, refname, sha1, oldval, flags,
-				   !!oldval)) ||
-	    (ref_transaction_commit(t, action, &err) && !(t = NULL))) {
+				   !!oldval) ||
+	    ref_transaction_commit(&t, action, &err)) {
 	     const char *str = "update_ref failed for ref '%s': %s";
 
 		ref_transaction_rollback(t);
@@ -3444,16 +3444,17 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 	return 0;
 }
 
-int ref_transaction_commit(struct ref_transaction *transaction,
+int ref_transaction_commit(struct ref_transaction **transaction,
 			   const char *msg, char **err)
 {
 	int ret = 0, delnum = 0, i;
 	const char **delnames;
-	int n = transaction->nr;
-	struct ref_update **updates = transaction->updates;
+	int n = (*transaction)->nr;
+	struct ref_update **updates = (*transaction)->updates;
 
 	if (!n) {
-		ref_transaction_free(transaction);
+		ref_transaction_free(*transaction);
+		*transaction = NULL;
 		return 0;
 	}
 
@@ -3527,7 +3528,8 @@ cleanup:
 		if (updates[i]->lock)
 			unlock_ref(updates[i]->lock);
 	free(delnames);
-	ref_transaction_free(transaction);
+	ref_transaction_free(*transaction);
+	*transaction = NULL;
 	return ret;
 }
 
diff --git a/refs.h b/refs.h
index 8135131..85127f2 100644
--- a/refs.h
+++ b/refs.h
@@ -270,8 +270,9 @@ int ref_transaction_delete(struct ref_transaction *transaction,
  * problem.  The ref_transaction is freed by this function.
  * If error is non-NULL it will return an error string that describes
  * why a commit failed. This string must be free()ed by the caller.
+ * *transaction is reset to NULL in this call.
  */
-int ref_transaction_commit(struct ref_transaction *transaction,
+int ref_transaction_commit(struct ref_transaction **transaction,
 			   const char *msg, char **err);
 
 /** Lock a ref and then write its file */
diff --git a/sequencer.c b/sequencer.c
index 7d59f58..3f6eced 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -283,11 +283,10 @@ static int fast_forward_to(const unsigned char *to, const unsigned char *from,
 	strbuf_addf(&sb, "%s: fast-forward", action_name(opts));
 
 	transaction = ref_transaction_begin();
-	if ((!transaction ||
+	if (!transaction ||
 	    ref_transaction_update(transaction, "HEAD", to, from,
-				   0, !unborn)) ||
-	    (ref_transaction_commit(transaction, sb.buf, &err) &&
-	     !(transaction = NULL))) {
+				   0, !unborn) ||
+	    ref_transaction_commit(&transaction, sb.buf, &err)) {
 		ref_transaction_rollback(transaction);
 		strbuf_release(&sb);
 		return error(_("HEAD: Could not fast-forward: %s\n"), err);
-- 
1.9.1.521.g5dc89fa