git-name-rev: add a --(no-)undefined option.

Rework get_rev_name to return NULL rather than "undefined" when a
reference is undefined. If --undefined is passed (default), git-name-rev
prints "undefined" for the name, else it die()s.

Make git-describe use --no-undefined when calling git-name-rev so
that --contains behavior matches the standard git-describe one.
Signed-off-by: NPierre Habouzit <madcoder@debian.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-describe.c

@@ -271,10 +271,11 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 	save_commit_buffer = 0;
 
 	if (contains) {
-		const char **args = xmalloc((5 + argc) * sizeof(char*));
+		const char **args = xmalloc((6 + argc) * sizeof(char*));
 		int i = 0;
 		args[i++] = "name-rev";
 		args[i++] = "--name-only";
+		args[i++] = "--no-undefined";
 		if (!all) {
 			args[i++] = "--tags";
 			if (pattern) {

builtin-name-rev.c

@@ -125,18 +125,18 @@ static int name_ref(const char *path, const unsigned char *sha1, int flags, void
 }
 
 /* returns a static buffer */
-static const char* get_rev_name(struct object *o)
+static const char *get_rev_name(struct object *o)
 {
 	static char buffer[1024];
 	struct rev_name *n;
 	struct commit *c;
 
 	if (o->type != OBJ_COMMIT)
-		return "undefined";
+		return NULL;
 	c = (struct commit *) o;
 	n = c->util;
 	if (!n)
-		return "undefined";
+		return NULL;
 
 	if (!n->generation)
 		return n->tip_name;
@@ -159,7 +159,7 @@ static char const * const name_rev_usage[] = {
 int cmd_name_rev(int argc, const char **argv, const char *prefix)
 {
 	struct object_array revs = { 0, 0, NULL };
-	int all = 0, transform_stdin = 0;
+	int all = 0, transform_stdin = 0, allow_undefined = 1;
 	struct name_ref_data data = { 0, 0, NULL };
 	struct option opts[] = {
 		OPT_BOOLEAN(0, "name-only", &data.name_only, "print only names (no SHA-1)"),
@@ -169,6 +169,7 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
 		OPT_GROUP(""),
 		OPT_BOOLEAN(0, "all", &all, "list all commits reachable from all refs"),
 		OPT_BOOLEAN(0, "stdin", &transform_stdin, "read from stdin"),
+		OPT_BOOLEAN(0, "undefined", &allow_undefined, "allow to print `undefined` names"),
 		OPT_END(),
 	};
 
@@ -226,7 +227,7 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
 				else if (++forty == 40 &&
 						!ishex(*(p+1))) {
 					unsigned char sha1[40];
-					const char *name = "undefined";
+					const char *name = NULL;
 					char c = *(p+1);
 
 					forty = 0;
@@ -240,11 +241,10 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
 					}
 					*(p+1) = c;
 
-					if (!strcmp(name, "undefined"))
+					if (!name)
 						continue;
 
-					fwrite(p_start, p - p_start + 1, 1,
-					       stdout);
+					fwrite(p_start, p - p_start + 1, 1, stdout);
 					printf(" (%s)", name);
 					p_start = p + 1;
 				}
@@ -260,18 +260,32 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
 		max = get_max_object_index();
 		for (i = 0; i < max; i++) {
 			struct object * obj = get_indexed_object(i);
+			const char *name;
 			if (!obj)
 				continue;
 			if (!data.name_only)
 				printf("%s ", sha1_to_hex(obj->sha1));
-			printf("%s\n", get_rev_name(obj));
+			name = get_rev_name(obj);
+			if (name)
+				printf("%s\n", name);
+			else if (allow_undefined)
+				printf("undefined\n");
+			else
+				die("cannot describe '%s'", sha1_to_hex(obj->sha1));
 		}
 	} else {
 		int i;
 		for (i = 0; i < revs.nr; i++) {
+			const char *name;
 			if (!data.name_only)
 				printf("%s ", revs.objects[i].name);
-			printf("%s\n", get_rev_name(revs.objects[i].item));
+			name = get_rev_name(revs.objects[i].item);
+			if (name)
+				printf("%s\n", name);
+			else if (allow_undefined)
+				printf("undefined\n");
+			else
+				die("cannot describe '%s'", sha1_to_hex(revs.objects[i].item->sha1));
 		}
 	}