The contributions we made to the Git 2.43 release

GitLab's Git team contributed several features and fixes to Git 2.43: - Added `--filter` and `--filter-to` options to `git repack` for segmenting objects across packfiles, enabling storage optimizations. - Added the `--exists` option to `git show` for a generic way to check object existence, crucial for the reftable backend. - Extended the `--missing` option in `git rev-list` to work with commit objects, supporting Gitaly's next-generation repository replication. - Enabled `gitattributes` to read from HEAD by default in bare repositories, reducing tech debt in Gitaly. - Fixed a bug in `git rev-list --stdin`. - Addressed an issue in commit-graphs where parsed commits weren't always checked for existence, introducing `GIT_COMMIT_GRAPH_PARANOIA`.