[0/2] When fetching, warn if in commit graph but not obj db

Message

Jonathan Tan Oct. 29, 2024, 9:11 p.m. UTC

I mentioned previously [1] the possibility of not running maintenance
steps (commit graph writing and "git maintenance") if no packs were
fetched, but looking at things again, I think that we shouldn't do
that - in particular, if I ran "git fetch --refetch", I would fully
expect the objects to be repacked, even if Git wasn't able to detect
conclusively whether a pack was transmitted.

So I went back to my original idea of detecting when an object is
missing. In trying to balance the concerns of both doing something as
reasonable as possible in such a repo corruption case, and not slowing
down and/or unnecessarily complicating the main code flow, I decided
to detect when an object is present in the commit graph but not in the
object DB, and to limit this detection for objects specified in the
fetch refspec.

Upon detection, we can't fix it due to reasons mentioned in the commit
message, so I decided to print a warning. An alternate option is to make
it a fatal error (instead of a warning) if an object is detected to be
in the commit graph but not the object DB. I haven't thought through the
ramifications of that, though.

[1] https://lore.kernel.org/git/[e-mail]/

Jonathan Tan (2):
  Revert "fetch-pack: add a deref_without_lazy_fetch_extended()"
  fetch-pack: warn if in commit graph but not obj db

 fetch-pack.c | 45 +++++++++++++++++++++++++--------------------
 object.h     |  2 +-
 2 files changed, 26 insertions(+), 21 deletions(-)