name-rev: don't xstrdup() an already dup'd string

When "add_to_tip_table()" is called with a non-zero
"shorten_unambiguous" we always return an xstrdup()'d string, which
we'd then xstrdup() again, leaking memory. See [1] and [2] for how
this leak came about.

We could xstrdup() only if "shorten_unambiguous" wasn't true, but
let's instead inline this code, so that information on whether we need
to xstrdup() is contained within add_to_tip_table().

1. 98c5c4a (name-rev: allow to specify a subpath for --refs
   option, 2013-06-18)
2. b23e0b9 (name-rev: allow converting the exact object name at
   the tip of a ref, 2013-07-07)

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

builtin/name-rev.c

@@ -273,17 +273,6 @@ static int subpath_matches(const char *path, const char *filter)
 	return -1;
 }
 
-static const char *name_ref_abbrev(const char *refname, int shorten_unambiguous)
-{
-	if (shorten_unambiguous)
-		refname = shorten_unambiguous_ref(refname, 0);
-	else if (skip_prefix(refname, "refs/heads/", &refname))
-		; /* refname already advanced */
-	else
-		skip_prefix(refname, "refs/", &refname);
-	return refname;
-}
-
 struct name_ref_data {
 	int tags_only;
 	int name_only;
@@ -309,11 +298,19 @@ static void add_to_tip_table(const struct object_id *oid, const char *refname,
 			     int shorten_unambiguous, struct commit *commit,
 			     timestamp_t taggerdate, int from_tag, int deref)
 {
-	refname = name_ref_abbrev(refname, shorten_unambiguous);
+	char *short_refname = NULL;
+
+	if (shorten_unambiguous)
+		short_refname = shorten_unambiguous_ref(refname, 0);
+	else if (skip_prefix(refname, "refs/heads/", &refname))
+		; /* refname already advanced */
+	else
+		skip_prefix(refname, "refs/", &refname);
 
 	ALLOC_GROW(tip_table.table, tip_table.nr + 1, tip_table.alloc);
 	oidcpy(&tip_table.table[tip_table.nr].oid, oid);
-	tip_table.table[tip_table.nr].refname = xstrdup(refname);
+	tip_table.table[tip_table.nr].refname = short_refname ?
+		short_refname : xstrdup(refname);
 	tip_table.table[tip_table.nr].commit = commit;
 	tip_table.table[tip_table.nr].taggerdate = taggerdate;
 	tip_table.table[tip_table.nr].from_tag = from_tag;