branch: report invalid tracking branch as gone

Command "git branch -vv" will report tracking branches, but invalid
tracking branches are also reported. This is because the function
stat_tracking_info() can not distinguish invalid tracking branch
from other cases which it would not like to report, such as
there is no upstream settings at all, or nothing is changed between
one branch and its upstream.

Junio suggested missing upstream should be reported [1] like:

    $ git branch -v -v
      master    e67ac84 initial
    * topic     3fc0f2a [topicbase: gone] topic

    $ git status
    # On branch topic
    # Your branch is based on 'topicbase', but the upstream is gone.
    #   (use "git branch --unset-upstream" to fixup)
    ...

    $ git status -b -s
    ## topic...topicbase [gone]
    ...

In order to do like that, we need to distinguish these three cases
(i.e. no tracking, with configured but no longer valid tracking, and
with tracking) in function stat_tracking_info(). So the refactored
function stat_tracking_info() has three return values: -1 (with "gone"
base), 0 (no base), and 1 (with base).

If the caller does not like to report tracking info when nothing
changed between the branch and its upstream, simply checks if
num_theirs and num_ours are both 0.

[1]: http://thread.gmane.org/gmane.comp.version-control.git/231830/focus=232288

Suggested-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 53 insertions, 4 deletions

diff --git a/t/t6040-tracking-info.sh b/t/t6040-tracking-info.sh
index ec2b516c3..6f678a4dc 100755
--- a/t/t6040-tracking-info.sh
+++ b/t/t6040-tracking-info.sh
@@ -28,10 +28,14 @@ test_expect_success setup '
 		git reset --hard HEAD^ &&
 		git checkout -b b4 origin &&
 		advance e &&
-		advance f
+		advance f &&
+		git checkout -b brokenbase origin &&
+		git checkout -b b5 --track brokenbase &&
+		advance g &&
+		git branch -d brokenbase
 	) &&
 	git checkout -b follower --track master &&
-	advance g
+	advance h
 '
 
 script='s/^..\(b.\)[	 0-9a-f]*\[\([^]]*\)\].*/\1 \2/p'
@@ -56,6 +60,7 @@ 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 brokenbase: gone
 EOF
 
 test_expect_success 'branch -vv' '
@@ -67,7 +72,7 @@ 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 &&
@@ -80,7 +85,15 @@ test_expect_success 'checkout with local tracked branch' '
 	test_i18ngrep "is ahead of" actual
 '
 
-test_expect_success 'status' '
+test_expect_success 'checkout (upstream is gone)' '
+	(
+		cd test &&
+		git checkout b5
+	) >actual &&
+	test_i18ngrep "is based on .*, but the upstream is gone." actual
+'
+
+test_expect_success 'status (diverged from upstream)' '
 	(
 		cd test &&
 		git checkout b1 >/dev/null &&
@@ -90,6 +103,42 @@ test_expect_success 'status' '
 	test_i18ngrep "have 1 and 1 different" actual
 '
 
+test_expect_success 'status (upstream is gone)' '
+	(
+		cd test &&
+		git checkout b5 >/dev/null &&
+		# reports nothing to commit
+		test_must_fail git commit --dry-run
+	) >actual &&
+	test_i18ngrep "is based on .*, but the upstream is gone." 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...brokenbase [gone]
+EOF
+
+test_expect_success 'status -s -b (upstream is gone)' '
+	(
+		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 &&