Makefile: Add custom patch to fix pathological perf with bitmap indices
With commit eccda331 (blob: Enable use of bitmap indices when searching
LFS pointers, 2021-03-11), we have added a feature flag which allows the
use of bitmap indices to accelerate searching for LFS pointers. As it
turns out, our usage of git-rev-list(1) triggered a pathological edge
case when adding negative tags to its invocation when bitmap indices are
in use. This issue was fixed upstream with commit 540cdc11ad
(pack-bitmap: avoid traversal of objects referenced by uninteresting
tag, 2021-03-22), which has recently been merged to git's next branch.
Add the patch such that we can reenable the use of bitmap indices and add more tests to verify that the since then newly added ListLFSPointers and ListAllLFSPointers RPCs behave well with bitmap indices.
This is kind of a test balloon for adding custom patches to Gitaly's make git target. I have documented a new process on which I'd like to get some feedback. The bar I've set is high: no patches get accepted which are not part of git's next branch, which is kind of what we agreed on during last week's team meeting. Furthermore, we mustn't assume that a patched-in feature is always available because there may always be unofficial distros or source-based installs which do not have these patches.
Let me know what you think.