Merge branch 'ti/checkout-track-failure'

The 'git switch' and 'git checkout' commands have been updated to
complete the branch switch instead of aborting when the tracking
configuration fails to write, matching the behavior of 'git push -u'.

* ti/checkout-track-failure:
  checkout: finish switching when the tracking config cannot be written
  branch: return an error from setup_tracking()

branch.c

@@ -251,12 +251,13 @@ static int inherit_tracking(struct tracking *tracking, const char *orig_ref)
  * will not be expanded to "refs/remotes/origin/main", so it is not safe
  * for 'orig_ref' to be raw user input.
  */
-static void setup_tracking(const char *new_ref, const char *orig_ref,
-			   enum branch_track track, int quiet)
+static int setup_tracking(const char *new_ref, const char *orig_ref,
+			  enum branch_track track, int quiet)
 {
 	struct tracking tracking;
 	struct string_list tracking_srcs = STRING_LIST_INIT_DUP;
 	int config_flags = quiet ? 0 : BRANCH_CONFIG_VERBOSE;
+	int ret = 0;
 	struct find_tracked_branch_cb ftb_cb = {
 		.tracking = &tracking,
 		.ambiguous_remotes = STRING_LIST_INIT_DUP,
@@ -345,11 +346,12 @@ static void setup_tracking(const char *new_ref, const char *orig_ref,
 		string_list_append(tracking.srcs, orig_ref);
 	if (install_branch_config_multiple_remotes(config_flags, new_ref,
 				tracking.remote, tracking.srcs) < 0)
-		exit(1);
+		ret = -1;
 
 cleanup:
 	string_list_clear(&tracking_srcs, 0);
 	string_list_clear(&ftb_cb.ambiguous_remotes, 0);
+	return ret;
 }
 
 int read_branch_desc(struct strbuf *buf, const char *branch_name)
@@ -629,10 +631,10 @@ static void dwim_branch_start(struct repository *r, const char *start_name,
 	FREE_AND_NULL(real_ref);
 }
 
-void create_branch(struct repository *r,
-		   const char *name, const char *start_name,
-		   int force, int clobber_head_ok, int reflog,
-		   int quiet, enum branch_track track, int dry_run)
+int create_branch(struct repository *r,
+		  const char *name, const char *start_name,
+		  int force, int clobber_head_ok, int reflog,
+		  int quiet, enum branch_track track, int dry_run)
 {
 	struct object_id oid;
 	char *real_ref;
@@ -641,6 +643,7 @@ void create_branch(struct repository *r,
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 	int flags = 0;
+	int ret = 0;
 	char *msg;
 
 	if (track == BRANCH_TRACK_OVERRIDE)
@@ -678,21 +681,25 @@ void create_branch(struct repository *r,
 	free(msg);
 
 	if (real_ref && track)
-		setup_tracking(ref.buf + 11, real_ref, track, quiet);
+		ret = setup_tracking(ref.buf + 11, real_ref, track, quiet);
 
 cleanup:
 	strbuf_release(&ref);
 	free(real_ref);
+	return ret;
 }
 
-void dwim_and_setup_tracking(struct repository *r, const char *new_ref,
-			     const char *orig_ref, enum branch_track track,
-			     int quiet)
+int dwim_and_setup_tracking(struct repository *r, const char *new_ref,
+			    const char *orig_ref, enum branch_track track,
+			    int quiet)
 {
 	char *real_orig_ref = NULL;
+	int ret;
+
 	dwim_branch_start(r, orig_ref, track, &real_orig_ref, NULL);
-	setup_tracking(new_ref, real_orig_ref, track, quiet);
+	ret = setup_tracking(new_ref, real_orig_ref, track, quiet);
 	free(real_orig_ref);
+	return ret;
 }
 
 /**
@@ -842,8 +849,8 @@ void create_branches_recursively(struct repository *r, const char *name,
 	 * tedious to determine whether or not tracking was set up in the
 	 * superproject.
 	 */
-	if (track)
-		setup_tracking(name, tracking_name, track, quiet);
+	if (track && setup_tracking(name, tracking_name, track, quiet))
+		exit(1);
 
 	for (i = 0; i < submodule_entry_list.entry_nr; i++) {
 		if (submodule_create_branch(

branch.h

@@ -34,10 +34,13 @@ enum branch_track {
  *     causes new_ref to track whatever orig_ref tracks.
  *
  *   - quiet suppresses tracking information.
+ *
+ * Returns 0 on success, or -1 if the tracking configuration could not be
+ * written.
  */
-void dwim_and_setup_tracking(struct repository *r, const char *new_ref,
-			     const char *orig_ref, enum branch_track track,
-			     int quiet);
+int dwim_and_setup_tracking(struct repository *r, const char *new_ref,
+			    const char *orig_ref, enum branch_track track,
+			    int quiet);
 
 /*
  * Creates a new branch, where:
@@ -63,12 +66,14 @@ void dwim_and_setup_tracking(struct repository *r, const char *new_ref,
  *
  *   - dry_run causes the branch to be validated but not created.
  *
+ * Returns 0 on success, or -1 if the tracking configuration could not be
+ * written.
  */
-void create_branch(struct repository *r,
-		   const char *name, const char *start_name,
-		   int force, int clobber_head_ok,
-		   int reflog, int quiet, enum branch_track track,
-		   int dry_run);
+int create_branch(struct repository *r,
+		  const char *name, const char *start_name,
+		  int force, int clobber_head_ok,
+		  int reflog, int quiet, enum branch_track track,
+		  int dry_run);
 
 /*
  * Creates a new branch in a repository and its submodules (and its

builtin/branch.c

@@ -1253,9 +1253,13 @@ int cmd_branch(int argc,
 			die(_("branch '%s' does not exist"), branch->name);
 		}
 
-		dwim_and_setup_tracking(the_repository, branch->name,
-					new_upstream, BRANCH_TRACK_OVERRIDE,
-					quiet);
+		if (dwim_and_setup_tracking(the_repository, branch->name,
+					    new_upstream, BRANCH_TRACK_OVERRIDE,
+					    quiet)) {
+			strbuf_release(&buf);
+			ret = 1;
+			goto out;
+		}
 		strbuf_release(&buf);
 	} else if (unset_upstream) {
 		struct branch *branch;
@@ -1305,8 +1309,11 @@ int cmd_branch(int argc,
 			ret = 0;
 			goto out;
 		}
-		create_branch(the_repository, branch_name, start_name, force, 0,
-			      reflog, quiet, track, 0);
+		if (create_branch(the_repository, branch_name, start_name,
+				  force, 0, reflog, quiet, track, 0)) {
+			ret = 1;
+			goto out;
+		}
 	} else
 		usage_with_options(builtin_branch_usage, options);
 

builtin/checkout.c

@@ -1017,6 +1017,12 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 			free(refname);
 		}
 		else
+			/*
+			 * Not fatal: the error and hint have already been
+			 * shown, and like "push -u" and "clone" we finish
+			 * the switch instead of leaving HEAD on the old
+			 * branch with the worktree already updated.
+			 */
 			create_branch(the_repository,
 				      opts->new_branch, new_branch_info->name,
 				      opts->new_branch_force ? 1 : 0,

t/t2027-checkout-track.sh

@@ -47,6 +47,26 @@ test_expect_success 'checkout --track -b overrides autoSetupMerge=inherit' '
 	test_cmp_config refs/heads/main branch.b4.merge
 '
 
+test_expect_success 'checkout -b completes when tracking config cannot be written' '
+	test_when_finished "git update-ref -d refs/remotes/lockremote/lockbranch" &&
+	test_when_finished "git branch -D lock-new" &&
+	test_when_finished "git checkout main" &&
+	test_config remote.lockremote.url . &&
+	test_config remote.lockremote.fetch "+refs/heads/*:refs/remotes/lockremote/*" &&
+	git update-ref refs/remotes/lockremote/lockbranch one &&
+	test_when_finished "rm -f .git/config.lock" &&
+	>.git/config.lock &&
+	git -c core.configLockTimeout=0 \
+		checkout -b lock-new lockremote/lockbranch 2>err &&
+	test_grep "unable to write upstream branch configuration" err &&
+	echo refs/heads/lock-new >expect &&
+	git symbolic-ref HEAD >actual &&
+	test_cmp expect actual &&
+	git diff --cached --exit-code &&
+	rm -f .git/config.lock &&
+	test_must_fail git config branch.lock-new.remote
+'
+
 test_expect_success 'ambiguous tracking info' '
 	# Set up a few remote repositories
 	git init --bare --initial-branch=trunk src1 &&

t/t2060-switch.sh

@@ -146,6 +146,26 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'switch -c completes when tracking config cannot be written' '
+	test_when_finished "git update-ref -d refs/remotes/lockremote/lockbranch" &&
+	test_when_finished "git branch -D lock-new" &&
+	test_when_finished "git switch main" &&
+	test_config remote.lockremote.url . &&
+	test_config remote.lockremote.fetch "+refs/heads/*:refs/remotes/lockremote/*" &&
+	git update-ref refs/remotes/lockremote/lockbranch first-branch &&
+	test_when_finished "rm -f .git/config.lock" &&
+	>.git/config.lock &&
+	git -c core.configLockTimeout=0 \
+		switch -c lock-new lockremote/lockbranch 2>err &&
+	test_grep "unable to write upstream branch configuration" err &&
+	echo refs/heads/lock-new >expect &&
+	git symbolic-ref HEAD >actual &&
+	test_cmp expect actual &&
+	git diff --cached --exit-code &&
+	rm -f .git/config.lock &&
+	test_must_fail git config branch.lock-new.remote
+'
+
 test_expect_success 'switch back when temporarily detached and checked out elsewhere ' '
 	test_when_finished "
 		git worktree remove wt1 ||:

t/t3200-branch.sh

@@ -1105,6 +1105,19 @@ test_expect_success '--set-upstream-to hint uses short remote-tracking branch na
 	test_cmp_config refs/heads/hintbranch branch.hint-local.merge
 '
 
+test_expect_success 'branch with start point fails when tracking config cannot be written' '
+	test_when_finished "git branch -D lock-new || :" &&
+	test_when_finished "git update-ref -d refs/remotes/lockremote/lockbranch" &&
+	test_config remote.lockremote.url . &&
+	test_config remote.lockremote.fetch "+refs/heads/*:refs/remotes/lockremote/*" &&
+	git update-ref refs/remotes/lockremote/lockbranch HEAD &&
+	test_when_finished "rm -f .git/config.lock" &&
+	>.git/config.lock &&
+	test_must_fail git -c core.configLockTimeout=0 \
+		branch lock-new lockremote/lockbranch 2>err &&
+	test_grep "unable to write upstream branch configuration" err
+'
+
 test_expect_success 'use --set-upstream-to modify HEAD' '
 	test_config branch.main.remote foo &&
 	test_config branch.main.merge foo &&