symbolic-ref: teach "--[no-]recurse" option

Suppose you are managing many maintenance tracks in your project,
and some of the more recent ones are maint-2.36 and maint-2.37.
Further imagine that your project recently tagged the official 2.38
release, which means you would need to start maint-2.38 track soon,
by doing:

  $ git checkout -b maint-2.38 v2.38.0^0
  $ git branch --list 'maint-2.3[6-9]'
  * maint-2.38
    maint-2.36
    maint-2.37

So far, so good.  But it also is reasonable to want not to have to
worry about which maintenance track is the latest, by pointing a
more generic-sounding 'maint' branch at it, by doing:

  $ git symbolic-ref refs/heads/maint refs/heads/maint-2.38

which would allow you to say "whichever it is, check out the latest
maintenance track", by doing:

  $ git checkout maint
  $ git branch --show-current
  maint-2.38

It is arguably better to say that we are on 'maint-2.38' rather than
on 'maint', and "git merge/pull" would record "into maint-2.38" and
not "into maint", so I think what we have is a good behaviour.

One thing that is slightly irritating, however, is that I do not
think there is a good way (other than "cat .git/HEAD") to learn that
you checked out 'maint' to get into that state.  Just like the output
of "git branch --show-current" shows above, "git symbolic-ref HEAD"
would report 'refs/heads/maint-2.38', bypassing the intermediate
symbolic ref at 'refs/heads/maint' that is pointed at by HEAD.

The internal resolve_ref() API already has the necessary support for
stopping after resolving a single level of a symbolic-ref, and we
can expose it by adding a "--[no-]recurse" option to the command.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/t/t1401-symbolic-ref.sh b/t/t1401-symbolic-ref.sh
index 132a1b885a..773a6e8e01 100755
--- a/t/t1401-symbolic-ref.sh
+++ b/t/t1401-symbolic-ref.sh
@@ -163,4 +163,18 @@ test_expect_success 'symbolic-ref can resolve d/f name (ENOTDIR)' '
 	test_cmp expect actual
 '
 
+test_expect_success 'symbolic-ref pointing at another' '
+	git update-ref refs/heads/maint-2.37 HEAD &&
+	git symbolic-ref refs/heads/maint refs/heads/maint-2.37 &&
+	git checkout maint &&
+
+	git symbolic-ref HEAD >actual &&
+	echo refs/heads/maint-2.37 >expect &&
+	test_cmp expect actual &&
+
+	git symbolic-ref --no-recurse HEAD >actual &&
+	echo refs/heads/maint >expect &&
+	test_cmp expect actual
+'
+
 test_done