[PATCH v2 25/25] pack-objects: double-check options before discarding objects

[Jeff King <peff@peff.net>]

When we are given an expiration time like
--unpack-unreachable=2.weeks.ago, we avoid writing out old,
unreachable loose objects entirely, under the assumption
that running "prune" would simply delete them immediately
anyway. However, this is only valid if we computed the same
set of reachable objects as prune would.

In practice, this is the case, because only git-repack uses
the --unpack-unreachable option with an expiration, and it
always feeds as many objects into the pack as possible. But
we can double-check at runtime just to be sure.

Signed-off-by: Jeff King <peff@peff.net>
---
No test here, because the potential breakage cannot be seen by running
"git repack" (because it gives sane options), nor by just running "git
pack-objects" (you can convince it not explode a loose object, but then
you would have to reimplement the part of "git repack" where it deletes
all the packs except the one we just created). So really this would only
be protecting in practice against somebody who tried to reimplement
git-repack themselves (and I do not know of anybody who has done that).

 builtin/pack-objects.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 3dc9108..72589ed 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -2757,6 +2757,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 
 	if (keep_unreachable && unpack_unreachable)
 		die("--keep-unreachable and --unpack-unreachable are incompatible.");
+	if (!rev_list_all || !rev_list_reflog || !rev_list_index)
+		unpack_unreachable_expiration = 0;
 
 	if (!use_internal_rev_list || !pack_to_stdout || is_repository_shallow())
 		use_bitmap_index = 0;
-- 
2.1.2.596.g7379948