[PATCH 0/3] Integrate changed-path Bloom filters with 'git blame'

If the changed-path Bloom filters are relatively stable, then I propose trying to build upon them as a way to discover any deficiencies. Also, it's good to use them when we can.

The goal I set out to achieve was to use Bloom filters as much as possible in git blame. I think I have achieved most of that, except I did not integrate it with the -C mode. In that case, the blob-diff computation takes a majority of the computation time, so short-circuiting the tree diff using Bloom filters. Also, it's just really complicated. If someone else thinks there is an easy win there, then please go ahead and give it a try with the extra logic presented here in PATCH 3.

While I was playing around with Bloom filters and git blame, I purposefully got it working with some scenarios but not all. Then I tried to trigger a failing build in the blame tests using GIT_TEST_COMMIT_GRAPH=1 and GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=1. But the tests all succeeded!

Examining the data, I see that the commit-graph didn't have the Bloom filter chunks at all. This is because we are not setting the flag to write them in the right spot. The GIT_TEST_COMMIT_GRAPH=1 variable triggers a commit-graph write during git commit, so we need to update the code there instead of just inspecting the variable in git commit-graph write. (This is PATCH 2.)

By updating this variable, I saw some test failures in other tests regarding non-exact pathspecs. I fixed these in PATCH 1 so we keep clean builds.

I based this change on [1] but it would apply cleanly (and logically) on gs/commit-graph-path-filter

Thanks, -Stolee

[1] https://lore.kernel.org/git/pull.601.v2.git.1586437211842.gitgitgadget@gmail.com/

Derrick Stolee (3):
  revision: complicated pathspecs disable filters
  commit: write commit-graph with bloom filters
  blame: use changed-path Bloom filters

 blame.c          | 139 ++++++++++++++++++++++++++++++++++++++++++++---
 blame.h          |   6 ++
 builtin/blame.c  |  10 ++++
 builtin/commit.c |   4 +-
 revision.c       |   9 +++
 5 files changed, 158 insertions(+), 10 deletions(-)

base-commit: f4df00a0dd448edce0e854a97f63598fefe27d27
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-609%2Fderrickstolee%2Fbloom-blame-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-609/derrickstolee/bloom-blame-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/609