Merge branch 'cn/branch-set-upstream-to'

"git branch --set-upstream origin/master" is a common mistake to
create a local branch 'origin/master' and set it to integrate with
the current branch.  With a plan to deprecate this option, introduce
"git branch (-u|--set-upstream-to) origin/master" that sets the
current branch to integrate with 'origin/master' remote tracking
branch.

* cn/branch-set-upstream-to:
  branch: deprecate --set-upstream and show help if we detect possible mistaken use
  branch: add --unset-upstream option
  branch: introduce --set-upstream-to

Documentation/git-branch.txt

@@ -13,6 +13,8 @@ SYNOPSIS
 	[--column[=<options>] | --no-column]
 	[(--merged | --no-merged | --contains) [<commit>]] [<pattern>...]
 'git branch' [--set-upstream | --track | --no-track] [-l] [-f] <branchname> [<start-point>]
+'git branch' (--set-upstream-to=<upstream> | -u <upstream>) [<branchname>]
+'git branch' --unset-upstream [<branchname>]
 'git branch' (-m | -M) [<oldbranch>] <newbranch>
 'git branch' (-d | -D) [-r] <branchname>...
 'git branch' --edit-description [<branchname>]
@@ -48,7 +50,7 @@ branch so that 'git pull' will appropriately merge from
 the remote-tracking branch. This behavior may be changed via the global
 `branch.autosetupmerge` configuration flag. That setting can be
 overridden by using the `--track` and `--no-track` options, and
-changed later using `git branch --set-upstream`.
+changed later using `git branch --set-upstream-to`.
 
 With a `-m` or `-M` option, <oldbranch> will be renamed to <newbranch>.
 If <oldbranch> had a corresponding reflog, it is renamed to match
@@ -173,6 +175,16 @@ start-point is either a local or remote-tracking branch.
 	like `--track` would when creating the branch, except that where
 	branch points to is not changed.
 
+-u <upstream>::
+--set-upstream-to=<upstream>::
+	Set up <branchname>'s tracking information so <upstream> is
+	considered <branchname>'s upstream branch. If no <branchname>
+	is specified, then it defaults to the current branch.
+
+--unset-upstream::
+	Remove the upstream information for <branchname>. If no branch
+	is specified it defaults to the current branch.
+
 --edit-description::
 	Open an editor and edit the text to explain what the branch is
 	for, to be used by various other commands (e.g. `request-pull`).

builtin/branch.c

@@ -714,7 +714,8 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	int delete = 0, rename = 0, force_create = 0, list = 0;
 	int verbose = 0, abbrev = -1, detached = 0;
 	int reflog = 0, edit_description = 0;
-	int quiet = 0;
+	int quiet = 0, unset_upstream = 0;
+	const char *new_upstream = NULL;
 	enum branch_track track;
 	int kinds = REF_LOCAL_BRANCH;
 	struct commit_list *with_commit = NULL;
@@ -728,6 +729,8 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 			BRANCH_TRACK_EXPLICIT),
 		OPT_SET_INT( 0, "set-upstream",  &track, N_("change upstream info"),
 			BRANCH_TRACK_OVERRIDE),
+		OPT_STRING('u', "set-upstream-to", &new_upstream, "upstream", "change the upstream info"),
+		OPT_BOOLEAN(0, "unset-upstream", &unset_upstream, "Unset the upstream info"),
 		OPT__COLOR(&branch_use_color, N_("use colored output")),
 		OPT_SET_INT('r', "remotes",     &kinds, N_("act on remote-tracking branches"),
 			REF_REMOTE_BRANCH),
@@ -796,10 +799,10 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, builtin_branch_usage,
 			     0);
 
-	if (!delete && !rename && !edit_description && argc == 0)
+	if (!delete && !rename && !edit_description && !new_upstream && !unset_upstream && argc == 0)
 		list = 1;
 
-	if (!!delete + !!rename + !!force_create + !!list > 1)
+	if (!!delete + !!rename + !!force_create + !!list + !!new_upstream + !!unset_upstream > 1)
 		usage_with_options(builtin_branch_usage, options);
 
 	if (abbrev == -1)
@@ -854,11 +857,62 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 			rename_branch(argv[0], argv[1], rename > 1);
 		else
 			usage_with_options(builtin_branch_usage, options);
+	} else if (new_upstream) {
+		struct branch *branch = branch_get(argv[0]);
+
+		if (!ref_exists(branch->refname))
+			die(_("branch '%s' does not exist"), branch->name);
+
+		/*
+		 * create_branch takes care of setting up the tracking
+		 * info and making sure new_upstream is correct
+		 */
+		create_branch(head, branch->name, new_upstream, 0, 0, 0, quiet, BRANCH_TRACK_OVERRIDE);
+	} else if (unset_upstream) {
+		struct branch *branch = branch_get(argv[0]);
+		struct strbuf buf = STRBUF_INIT;
+
+		if (!branch_has_merge_config(branch)) {
+			die(_("Branch '%s' has no upstream information"), branch->name);
+		}
+
+		strbuf_addf(&buf, "branch.%s.remote", branch->name);
+		git_config_set_multivar(buf.buf, NULL, NULL, 1);
+		strbuf_reset(&buf);
+		strbuf_addf(&buf, "branch.%s.merge", branch->name);
+		git_config_set_multivar(buf.buf, NULL, NULL, 1);
+		strbuf_release(&buf);
 	} else if (argc > 0 && argc <= 2) {
+		struct branch *branch = branch_get(argv[0]);
+		int branch_existed = 0, remote_tracking = 0;
+		struct strbuf buf = STRBUF_INIT;
+
 		if (kinds != REF_LOCAL_BRANCH)
 			die(_("-a and -r options to 'git branch' do not make sense with a branch name"));
+
+		if (track == BRANCH_TRACK_OVERRIDE)
+			fprintf(stderr, _("The --set-upstream flag is deprecated and will be removed. Consider using --track or --set-upstream-to\n"));
+
+		strbuf_addf(&buf, "refs/remotes/%s", branch->name);
+		remote_tracking = ref_exists(buf.buf);
+		strbuf_release(&buf);
+
+		branch_existed = ref_exists(branch->refname);
 		create_branch(head, argv[0], (argc == 2) ? argv[1] : head,
 			      force_create, reflog, 0, quiet, track);
+
+		/*
+		 * We only show the instructions if the user gave us
+		 * one branch which doesn't exist locally, but is the
+		 * name of a remote-tracking branch.
+		 */
+		if (argc == 1 && track == BRANCH_TRACK_OVERRIDE &&
+		    !branch_existed && remote_tracking) {
+			fprintf(stderr, _("\nIf you wanted to make '%s' track '%s', do this:\n\n"), head, branch->name);
+			fprintf(stderr, _("    git branch -d %s\n"), branch->name);
+			fprintf(stderr, _("    git branch --set-upstream-to %s\n"), branch->name);
+		}
+
 	} else
 		usage_with_options(builtin_branch_usage, options);
 

t/t3200-branch.sh

@@ -369,6 +369,76 @@ test_expect_success \
     'git tag foobar &&
      test_must_fail git branch --track my11 foobar'
 
+test_expect_success 'use --set-upstream-to modify HEAD' \
+    'test_config branch.master.remote foo &&
+     test_config branch.master.merge foo &&
+     git branch my12
+     git branch --set-upstream-to my12 &&
+     test "$(git config branch.master.remote)" = "." &&
+     test "$(git config branch.master.merge)" = "refs/heads/my12"'
+
+test_expect_success 'use --set-upstream-to modify a particular branch' \
+    'git branch my13
+     git branch --set-upstream-to master my13 &&
+     test "$(git config branch.my13.remote)" = "." &&
+     test "$(git config branch.my13.merge)" = "refs/heads/master"'
+
+test_expect_success '--unset-upstream should fail if given a non-existent branch' \
+    'test_must_fail git branch --unset-upstream i-dont-exist'
+
+test_expect_success 'test --unset-upstream on HEAD' \
+    'git branch my14
+     test_config branch.master.remote foo &&
+     test_config branch.master.merge foo &&
+     git branch --set-upstream-to my14 &&
+     git branch --unset-upstream &&
+     test_must_fail git config branch.master.remote &&
+     test_must_fail git config branch.master.merge &&
+     # fail for a branch without upstream set
+     test_must_fail git branch --unset-upstream
+'
+
+test_expect_success 'test --unset-upstream on a particular branch' \
+    'git branch my15
+     git branch --set-upstream-to master my14 &&
+     git branch --unset-upstream my14 &&
+     test_must_fail git config branch.my14.remote &&
+     test_must_fail git config branch.my14.merge'
+
+test_expect_success '--set-upstream shows message when creating a new branch that exists as remote-tracking' \
+    'git update-ref refs/remotes/origin/master HEAD &&
+     git branch --set-upstream origin/master 2>actual &&
+     test_when_finished git update-ref -d refs/remotes/origin/master &&
+     test_when_finished git branch -d origin/master &&
+     cat >expected <<EOF &&
+The --set-upstream flag is deprecated and will be removed. Consider using --track or --set-upstream-to
+
+If you wanted to make '"'master'"' track '"'origin/master'"', do this:
+
+    git branch -d origin/master
+    git branch --set-upstream-to origin/master
+EOF
+     test_cmp expected actual
+'
+
+test_expect_success '--set-upstream with two args only shows the deprecation message' \
+    'git branch --set-upstream master my13 2>actual &&
+     test_when_finished git branch --unset-upstream master &&
+     cat >expected <<EOF &&
+The --set-upstream flag is deprecated and will be removed. Consider using --track or --set-upstream-to
+EOF
+     test_cmp expected actual
+'
+
+test_expect_success '--set-upstream with one arg only shows the deprecation message if the branch existed' \
+    'git branch --set-upstream my13 2>actual &&
+     test_when_finished git branch --unset-upstream my13 &&
+     cat >expected <<EOF &&
+The --set-upstream flag is deprecated and will be removed. Consider using --track or --set-upstream-to
+EOF
+     test_cmp expected actual
+'
+
 # Keep this test last, as it changes the current branch
 cat >expect <<EOF
 $_z40 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	branch: Created from master