rev-list: extend print-info to print missing object type

Additional information about missing objects found in git-rev-list(1)
can be printed by specifying the `print-info` missing action for the
`--missing` option. Extend this action to also print missing object type
information inferred from its containing object. This token follows the
form `type=<type>` and specifies the expected object type of the missing
object.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Acked-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/rev-list-options.txt

@@ -1038,6 +1038,9 @@ one of the following:
 * The `path=<path>` shows the path of the missing object inferred from a
   containing object. A path containing SP or special characters is enclosed in
   double-quotes in the C style as needed.
++
+* The `type=<type>` shows the type of the missing object inferred from a
+  containing object.
 --
 +
 If some tips passed to the traversal are missing, they will be

builtin/rev-list.c

@@ -79,6 +79,7 @@ static int arg_print_omitted; /* print objects omitted by filter */
 struct missing_objects_map_entry {
 	struct oidmap_entry entry;
 	const char *path;
+	unsigned type;
 };
 static struct oidmap missing_objects;
 enum missing_action {
@@ -109,7 +110,8 @@ static off_t get_object_disk_usage(struct object *obj)
 	return size;
 }
 
-static void add_missing_object_entry(struct object_id *oid, const char *path)
+static void add_missing_object_entry(struct object_id *oid, const char *path,
+				     unsigned type)
 {
 	struct missing_objects_map_entry *entry;
 
@@ -118,6 +120,7 @@ static void add_missing_object_entry(struct object_id *oid, const char *path)
 
 	CALLOC_ARRAY(entry, 1);
 	entry->entry.oid = *oid;
+	entry->type = type;
 	if (path)
 		entry->path = xstrdup(path);
 	oidmap_put(&missing_objects, entry);
@@ -142,6 +145,8 @@ static void print_missing_object(struct missing_objects_map_entry *entry,
 
 		strbuf_release(&path);
 	}
+	if (entry->type)
+		strbuf_addf(&sb, " type=%s", type_name(entry->type));
 
 	printf("?%s%s\n", oid_to_hex(&entry->entry.oid), sb.buf);
 	strbuf_release(&sb);
@@ -166,7 +171,7 @@ static inline void finish_object__ma(struct object *obj, const char *name)
 
 	case MA_PRINT:
 	case MA_PRINT_INFO:
-		add_missing_object_entry(&obj->oid, name);
+		add_missing_object_entry(&obj->oid, name, obj->type);
 		return;
 
 	case MA_ALLOW_PROMISOR:
@@ -843,7 +848,7 @@ int cmd_rev_list(int argc,
 
 		/* Add missing tips */
 		while ((oid = oidset_iter_next(&iter)))
-			add_missing_object_entry(oid, NULL);
+			add_missing_object_entry(oid, NULL, 0);
 
 		oidset_clear(&revs.missing_commits);
 	}

t/t6022-rev-list-missing.sh

@@ -164,6 +164,7 @@ do
 
 			oid="$(git rev-parse "$obj")" &&
 			path=".git/objects/$(test_oid_to_path $oid)" &&
+			type_info=" type=$(git cat-file -t $oid)" &&
 
 			case $obj in
 			HEAD:foo)
@@ -184,7 +185,7 @@ do
 			# get the expected oids.
 			git rev-list --objects --no-object-names \
 				HEAD ^"$obj" >expect.raw &&
-			echo "?$oid$path_info" >>expect.raw &&
+			echo "?$oid$path_info$type_info" >>expect.raw &&
 
 			mv "$path" "$path.hidden" &&
 			git rev-list --objects --no-object-names \