format-patch: refactor branch name calculation

By moving the part that relies on rev->pending earlier, where we are
already checking the special case where there's only one ref.
Signed-off-by: NFelipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -1052,15 +1052,6 @@ static char *find_branch_name(struct rev_info *rev)
 	if (0 <= positive) {
 		ref = rev->cmdline.rev[positive].name;
 		tip_sha1 = rev->cmdline.rev[positive].item->sha1;
-	} else if (!rev->cmdline.nr && rev->pending.nr == 1 &&
-		   !strcmp(rev->pending.objects[0].name, "HEAD")) {
-		/*
-		 * No actual ref from command line, but "HEAD" from
-		 * rev->def was added in setup_revisions()
-		 * e.g. format-patch --cover-letter -12
-		 */
-		ref = "HEAD";
-		tip_sha1 = rev->pending.objects[0].item->sha1;
 	} else {
 		return NULL;
 	}
@@ -1280,28 +1271,36 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 	}
 
 	if (rev.pending.nr == 1) {
+		int check_head = 0;
+
 		if (rev.max_count < 0 && !rev.show_root_diff) {
 			/*
 			 * This is traditional behaviour of "git format-patch
 			 * origin" that prepares what the origin side still
 			 * does not have.
 			 */
-			unsigned char sha1[20];
-			const char *ref;
-
 			rev.pending.objects[0].item->flags |= UNINTERESTING;
 			add_head_to_pending(&rev);
-			ref = resolve_ref_unsafe("HEAD", sha1, 1, NULL);
-			if (ref && !prefixcmp(ref, "refs/heads/"))
-				branch_name = xstrdup(ref + strlen("refs/heads/"));
-			else
-				branch_name = xstrdup(""); /* no branch */
+			check_head = 1;
 		}
 		/*
 		 * Otherwise, it is "format-patch -22 HEAD", and/or
 		 * "format-patch --root HEAD".  The user wants
 		 * get_revision() to do the usual traversal.
 		 */
+
+		if (!strcmp(rev.pending.objects[0].name, "HEAD"))
+			check_head = 1;
+
+		if (check_head) {
+			unsigned char sha1[20];
+			const char *ref;
+			ref = resolve_ref_unsafe("HEAD", sha1, 1, NULL);
+			if (ref && !prefixcmp(ref, "refs/heads/"))
+				branch_name = xstrdup(ref + strlen("refs/heads/"));
+			else
+				branch_name = xstrdup(""); /* no branch */
+		}
 	}
 
 	/*