[PATCH 2/2] Protect commits recorded in reflog from pruning.

[Junio C Hamano <junkio@cox.net>]

This teaches fsck-objects and prune to protect objects referred
to by reflog entries.

Signed-off-by: Junio C Hamano <junkio@cox.net>
---

 >>  - now reflog is enabled by default for user repositories, I
 >>    have two worries about its effect, fortunately can be killed
 >>    with a single stone.
 >> 
 >>    * the reflog grows unbounded;
 >> 
 >>    * revisions recorded in the reflog can be pruned out,
 >>      rendering some entries in reflog useless.
 >> 
 >>    I am thinking about teaching fsck-objects and prune to keep
 >>    revisions recorded in the reflog; we would need an end-user
 >>    way to prune older reflog entries and I would appreciate
 >>    somebody codes it up, but even without it, people can always
 >>    use "vi" or "ed" on reflog files ;-).

 Rewinding would not lose any objects from the object database
 with this; somebody needs to code up a garbage collector and/or
 expiration mechanism for reflogs.

 builtin-prune.c |   16 ++++++++++++++++
 fsck-objects.c  |   22 ++++++++++++++++++++++
 2 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/builtin-prune.c b/builtin-prune.c
index 8591d28..00a53b3 100644
--- a/builtin-prune.c
+++ b/builtin-prune.c
@@ -181,12 +181,28 @@ static void walk_commit_list(struct rev_info *revs)
 	}
 }
 
+static int add_one_reflog_ent(unsigned char *osha1, unsigned char *nsha1, char *datail, void *cb_data)
+{
+	struct object *object;
+
+	object = parse_object(osha1);
+	if (object)
+		add_pending_object(&revs, object, "");
+	object = parse_object(nsha1);
+	if (object)
+		add_pending_object(&revs, object, "");
+	return 0;
+}
+
 static int add_one_ref(const char *path, const unsigned char *sha1, int flag, void *cb_data)
 {
 	struct object *object = parse_object(sha1);
 	if (!object)
 		die("bad object ref: %s:%s", path, sha1_to_hex(sha1));
 	add_pending_object(&revs, object, "");
+
+	for_each_reflog_ent(path, add_one_reflog_ent, NULL);
+
 	return 0;
 }
 
diff --git a/fsck-objects.c b/fsck-objects.c
index 46b628c..e3746e8 100644
--- a/fsck-objects.c
+++ b/fsck-objects.c
@@ -402,6 +402,25 @@ static void fsck_dir(int i, char *path)
 
 static int default_refs;
 
+static int fsck_handle_reflog_ent(unsigned char *osha1, unsigned char *nsha1, char *datail, void *cb_data)
+{
+	struct object *obj;
+
+	if (!is_null_sha1(osha1)) {
+		obj = lookup_object(osha1);
+		if (obj) {
+			obj->used = 1;
+			mark_reachable(obj, REACHABLE);
+		}
+	}
+	obj = lookup_object(nsha1);
+	if (obj) {
+		obj->used = 1;
+		mark_reachable(obj, REACHABLE);
+	}
+	return 0;
+}
+
 static int fsck_handle_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
 {
 	struct object *obj;
@@ -419,6 +438,9 @@ static int fsck_handle_ref(const char *refname, const unsigned char *sha1, int f
 	default_refs++;
 	obj->used = 1;
 	mark_reachable(obj, REACHABLE);
+
+	for_each_reflog_ent(refname, fsck_handle_reflog_ent, NULL);
+
 	return 0;
 }
 
-- 
1.4.4.2.gc30f