[PATCH 2/5] fast-export: do not refer to non-existing marks

[Sverre Rabbelier <srabbelier@gmail.com>]

From: Johannes Schindelin <Johannes.Schindelin@gmx.de>

When calling `git fast-export a..a b` when a and b refer to the same
commit, nothing would be exported, and an incorrect reset line would
be printed for b ('from :0').

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Sverre Rabbelier <srabbelier@gmail.com>
---

  We encountered this one while staring at the code and trying to
  figure out if our existing solution was sufficient.

 builtin/fast-export.c |   17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index becef85..92743c8 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -512,9 +512,20 @@ static void get_tags_and_duplicates(struct object_array *pending,
 	}
 }
 
+static void handle_reset(const char *name, struct object *object)
+{
+	int mark = get_object_mark(object);
+
+	if (mark)
+		printf("reset %s\nfrom :%d\n\n", name,
+		       get_object_mark(object));
+	else
+		printf("reset %s\nfrom %s\n\n", name,
+		       sha1_to_hex(object->sha1));
+}
+
 static void handle_tags_and_duplicates(struct string_list *extra_refs)
 {
-	struct commit *commit;
 	int i;
 
 	for (i = extra_refs->nr - 1; i >= 0; i--) {
@@ -526,9 +537,7 @@ static void handle_tags_and_duplicates(struct string_list *extra_refs)
 			break;
 		case OBJ_COMMIT:
 			/* create refs pointing to already seen commits */
-			commit = (struct commit *)object;
-			printf("reset %s\nfrom :%d\n\n", name,
-			       get_object_mark(&commit->object));
+			handle_reset(name, object);
 			show_progress();
 			break;
 		}
-- 
1.7.6.385.g91185.dirty