builtin/describe.c: rename `oid` to avoid variable shadowing

The function `describe` has already a variable named `oid` declared at
the beginning of the function for an object id.  Do not shadow that
variable with a pointer to an object id.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/describe.c

@@ -381,9 +381,9 @@ static void describe(const char *arg, int last_one)
 	}
 
 	if (!match_cnt) {
-		struct object_id *oid = &cmit->object.oid;
+		struct object_id *cmit_oid = &cmit->object.oid;
 		if (always) {
-			printf("%s", find_unique_abbrev(oid->hash, abbrev));
+			printf("%s", find_unique_abbrev(cmit_oid->hash, abbrev));
 			if (suffix)
 				printf("%s", suffix);
 			printf("\n");
@@ -392,11 +392,11 @@ static void describe(const char *arg, int last_one)
 		if (unannotated_cnt)
 			die(_("No annotated tags can describe '%s'.\n"
 			    "However, there were unannotated tags: try --tags."),
-			    oid_to_hex(oid));
+			    oid_to_hex(cmit_oid));
 		else
 			die(_("No tags can describe '%s'.\n"
 			    "Try --always, or create some tags."),
-			    oid_to_hex(oid));
+			    oid_to_hex(cmit_oid));
 	}
 
 	QSORT(all_matches, match_cnt, compare_pt);