[PATCH v3] status: always show tracking branch even no change

[Jiang Xin <worldhello.net@gmail.com>]

If the current branch has an upstream branch, and there are changes
between the current branch and its upstream, some commands (such as
"git status", "git status -bs", and "git checkout") will report their
relationship. E.g.

    $ git status
    # On branch master
    # Your branch is ahead of 'origin/master' by 1 commit.
    #   (use "git push" to publish your local commits)
    #
    ...

    $ git status -bs
    ## master...origin/master [ahead 1]
    ...

    $ git checkout master
    Already on 'master'
    Your branch is ahead of 'origin/master' by 1 commit.
      (use "git push" to publish your local commits)

But if there is no difference between the current branch and its
upstream, the relationship will not be reported, and it's hard to
tell whether the current branch has a tracking branch or not. And
what's worse, when the 'push.default' config variable is set to
`matching`, it's hard to tell whether the current branch has already
been pushed out or not at all [1].

So always show the remote tracking branch in the output of "git status"
and other commands will help users to see where the current branch
will push to and pull from. E.g.

    $ git status
    # On branch master
    # Your branch is identical to 'origin/master'.
    #
    ...

    $ git status -bs
    ## master...origin/master
    ...

    $ git checkout master
    Already on 'master'
    Your branch is identical to 'origin/master'.

This patch changes the return value of function stat_tracking_info().
When the current branch and its remote tracking branch point to the
same commit, will return 1, instead of 0. Because we want to report
the tracking info for such case. Also add some test cases in t6040.

[1]: http://thread.gmane.org/gmane.comp.version-control.git/198703

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
---
 builtin/branch.c         | 18 +++++-----------
 remote.c                 | 18 +++++++++++-----
 t/t6040-tracking-info.sh | 54 ++++++++++++++++++++++++++++++++++++++++++++----
 wt-status.c              |  5 +++++
 4 files changed, 73 insertions(+), 22 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 0836890..359e75d 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -424,19 +424,8 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 	struct branch *branch = branch_get(branch_name);
 	struct strbuf fancy = STRBUF_INIT;
 
-	if (!stat_tracking_info(branch, &ours, &theirs)) {
-		if (branch && branch->merge && branch->merge[0]->dst &&
-		    show_upstream_ref) {
-			ref = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
-			if (want_color(branch_use_color))
-				strbuf_addf(stat, "[%s%s%s] ",
-						branch_get_color(BRANCH_COLOR_UPSTREAM),
-						ref, branch_get_color(BRANCH_COLOR_RESET));
-			else
-				strbuf_addf(stat, "[%s] ", ref);
-		}
+	if (!stat_tracking_info(branch, &ours, &theirs))
 		return;
-	}
 
 	if (show_upstream_ref) {
 		ref = shorten_unambiguous_ref(branch->merge[0]->dst, 0);
@@ -448,7 +437,10 @@ static void fill_tracking_info(struct strbuf *stat, const char *branch_name,
 			strbuf_addstr(&fancy, ref);
 	}
 
-	if (!ours) {
+	if (!ours && !theirs) {
+		if (ref)
+			strbuf_addf(stat, _("[%s]"), fancy.buf);
+	} else if (!ours) {
 		if (ref)
 			strbuf_addf(stat, _("[%s: behind %d]"), fancy.buf, theirs);
 		else
diff --git a/remote.c b/remote.c
index 2433467..79766df 100644
--- a/remote.c
+++ b/remote.c
@@ -1740,6 +1740,10 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	const char *rev_argv[10], *base;
 	int rev_argc;
 
+	/* Set both num_theirs and num_ours as undetermined. */
+	*num_theirs = -1;
+	*num_ours = -1;
+
 	/*
 	 * Nothing to report unless we are marked to build on top of
 	 * somebody else.
@@ -1758,16 +1762,18 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	theirs = lookup_commit_reference(sha1);
 	if (!theirs)
 		return 0;
+	*num_theirs = 0;
 
 	if (read_ref(branch->refname, sha1))
 		return 0;
 	ours = lookup_commit_reference(sha1);
 	if (!ours)
 		return 0;
+	*num_ours = 0;
 
-	/* are we the same? */
+	/* are we the same? both num_theirs and num_ours have been set to 0. */
 	if (theirs == ours)
-		return 0;
+		return 1;
 
 	/* Run "rev-list --left-right ours...theirs" internally... */
 	rev_argc = 0;
@@ -1786,8 +1792,6 @@ int stat_tracking_info(struct branch *branch, int *num_ours, int *num_theirs)
 	prepare_revision_walk(&revs);
 
 	/* ... and count the commits on each side. */
-	*num_ours = 0;
-	*num_theirs = 0;
 	while (1) {
 		struct commit *c = get_revision(&revs);
 		if (!c)
@@ -1817,7 +1821,11 @@ int format_tracking_info(struct branch *branch, struct strbuf *sb)
 
 	base = branch->merge[0]->dst;
 	base = shorten_unambiguous_ref(base, 0);
-	if (!num_theirs) {
+	if (!num_ours && !num_theirs) {
+		strbuf_addf(sb,
+			_("Your branch is identical to '%s'.\n"),
+			base);
+	} else if (!num_theirs) {
 		strbuf_addf(sb,
 			Q_("Your branch is ahead of '%s' by %d commit.\n",
 			   "Your branch is ahead of '%s' by %d commits.\n",
diff --git a/t/t6040-tracking-info.sh b/t/t6040-tracking-info.sh
index ec2b516..eafce7d 100755
--- a/t/t6040-tracking-info.sh
+++ b/t/t6040-tracking-info.sh
@@ -28,18 +28,20 @@ test_expect_success setup '
 		git reset --hard HEAD^ &&
 		git checkout -b b4 origin &&
 		advance e &&
-		advance f
+		advance f &&
+		git checkout -b b5 origin
 	) &&
 	git checkout -b follower --track master &&
 	advance g
 '
 
-script='s/^..\(b.\)[	 0-9a-f]*\[\([^]]*\)\].*/\1 \2/p'
+script='s/^..\(b.\)[	 0-9a-f]*\(\[\([^]]*\)\]\)\{0,1\}.*/\1 \3/p'
 cat >expect <<\EOF
 b1 ahead 1, behind 1
 b2 ahead 1, behind 1
 b3 behind 1
 b4 ahead 2
+b5 
 EOF
 
 test_expect_success 'branch -v' '
@@ -56,6 +58,7 @@ b1 origin/master: ahead 1, behind 1
 b2 origin/master: ahead 1, behind 1
 b3 origin/master: behind 1
 b4 origin/master: ahead 2
+b5 origin/master
 EOF
 
 test_expect_success 'branch -vv' '
@@ -67,20 +70,27 @@ test_expect_success 'branch -vv' '
 	test_i18ncmp expect actual
 '
 
-test_expect_success 'checkout' '
+test_expect_success 'checkout (diverged from upstream)' '
 	(
 		cd test && git checkout b1
 	) >actual &&
 	test_i18ngrep "have 1 and 1 different" actual
 '
 
+test_expect_success 'checkout (identical to upstream)' '
+	(
+		cd test && git checkout b5
+	) >actual &&
+	test_i18ngrep "Your branch is identical to .origin/master" actual
+'
+
 test_expect_success 'checkout with local tracked branch' '
 	git checkout master &&
 	git checkout follower >actual &&
 	test_i18ngrep "is ahead of" actual
 '
 
-test_expect_success 'status' '
+test_expect_success 'status (diverged from upstream)' '
 	(
 		cd test &&
 		git checkout b1 >/dev/null &&
@@ -90,6 +100,42 @@ test_expect_success 'status' '
 	test_i18ngrep "have 1 and 1 different" actual
 '
 
+test_expect_success 'status (identical to upstream)' '
+	(
+		cd test &&
+		git checkout b5 >/dev/null &&
+		# reports nothing to commit
+		test_must_fail git commit --dry-run
+	) >actual &&
+	test_i18ngrep "Your branch is identical to .origin/master" actual
+'
+
+cat >expect <<\EOF
+## b1...origin/master [ahead 1, behind 1]
+EOF
+
+test_expect_success 'status -s -b (diverged from upstream)' '
+	(
+		cd test &&
+		git checkout b1 >/dev/null &&
+		git status -s -b | head -1
+	) >actual &&
+	test_i18ncmp expect actual
+'
+
+cat >expect <<\EOF
+## b5...origin/master
+EOF
+
+test_expect_success 'status -s -b (identical to upstream)' '
+	(
+		cd test &&
+		git checkout b5 >/dev/null &&
+		git status -s -b | head -1
+	) >actual &&
+	test_i18ncmp expect actual
+'
+
 test_expect_success 'fail to track lightweight tags' '
 	git checkout master &&
 	git tag light &&
diff --git a/wt-status.c b/wt-status.c
index ff4b324..39742ff 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -1392,6 +1392,11 @@ static void wt_shortstatus_print_tracking(struct wt_status *s)
 	color_fprintf(s->fp, header_color, "...");
 	color_fprintf(s->fp, branch_color_remote, "%s", base);
 
+	if (!num_ours && !num_theirs) {
+		fputc(s->null_termination ? '\0' : '\n', s->fp);
+		return;
+	}
+
 	color_fprintf(s->fp, header_color, " [");
 	if (!num_ours) {
 		color_fprintf(s->fp, header_color, _("behind "));
-- 
1.8.4.rc1.430.g417e2f3