rev-parse: fix parent shorthands with --symbolic

The try_parent_shorthands() function shows each parent via
show_rev(). We pass the correct parent sha1, but our "name"
parameter still points at the original refname. So asking
for a regular rev-parse works fine (it prints the sha1s),
but asking for the symbolic name gives nonsense like:

    $ git rev-parse --symbolic HEAD^-1
    HEAD
    ^HEAD

which is always an empty set of commits. Asking for "^!" is
likewise broken, with the added bonus that its prints ^HEAD
for _each_ parent. And "^@" just prints HEAD repeatedly.

Arguably it would be correct to just pass NULL as the name
here, and always get the parent expressed as a sha1. The
"--symbolic" documentaton claims only "as close to the
original input as possible", and we certainly fallback to
sha1s where necessary. But it's pretty easy to generate a
symbolic name on the fly from the original.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 4da1f1da25..c352f2f8b2 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -342,11 +342,16 @@ static int try_parent_shorthands(const char *arg)
 	for (parents = commit->parents, parent_number = 1;
 	     parents;
 	     parents = parents->next, parent_number++) {
+		char *name = NULL;
+
 		if (exclude_parent && parent_number != exclude_parent)
 			continue;
 
+		if (symbolic)
+			name = xstrfmt("%s^%d", arg, parent_number);
 		show_rev(include_parents ? NORMAL : REVERSED,
-			 parents->item->object.oid.hash, arg);
+			 parents->item->object.oid.hash, name);
+		free(name);
 	}
 
 	*dotdot = '^';