[PATCH RFC 0/5] Introduce git-blame-tree(1) command

This is another attempt to upstream the git-blame-tree(1) subcommand. After the previous attempt[1] the people of GitHub shared their version of the subcommand, and this version integrates those changes.

What is different from the series shared by GitHub:

* Patches for --max-depth are excluded. I think it's a separate topic to
  discuss and I'm not sure it needs to be part of blame-tree anyway. The
  main patch was submitted in the previous attempt[2] and if people
  consider it valuable, I'm happy to discuss that in a separate patch
  series.

* The patches in 'tb/blame-tree' at Taylor's fork[3] implements a
  caching layer. This feature reads/writes cached blame-tree results in
  `.git/blame-tree/<hash>.btc`. To keep this series to a reviewable
  size, that feature is excluded from this series. I think it's better
  to submit this as a separate series.

* Squashed various commits together. Like they introduced a flag
  `--go-faster`, which later became the default and only implementation.
  That story was wrapped up in a single commit.

* The blame-tree command isn't recursive by default. If you want recurse
  into subtrees, you need to pass `-r`.

* Fixed all memory leaks, and removed the use of
  USE_THE_REPOSITORY_VARIABLE.

I've attempted to reuse commit messages as good as possible, but feel free to correct me where you think I didn't give proper credit or messed up. Although I have no idea what to do with the Signed-off-by trailers.

I didn't modify the benchmark results in the commit messages, simply because I didn't get comparable results. In my benchmarks the difference between two implementations was negligible, and even in some scenarios the performance was worse in the "improved" implementation. As far as I can tell, I didn't break anything in my refactoring, because the version in these patches acts similar to Taylor's branch. To be honest, I cannot explain why...?

With this version I'd like to gather feedback as much as possible for a next version. I realize this feature is far from done, so that's why I'm submitting it as an RFC.

Again thanks to Taylor and the people at GitHub for sharing these patches. I hope we can work together to get this upstreamed.

[1]: https://lore.kernel.org/git/20250326-toon-blame-tree-v1-0-4173133f3786@iotcl.com/ [2]: https://lore.kernel.org/git/20250326-toon-blame-tree-v1-3-4173133f3786@iotcl.com/ [3]: git@github.com:ttaylorr/git.git

-- Toon

Signed-off-by: Toon Claes <toon@iotcl.com>
---
Jeff King (1):
      t/perf: add blame-tree perf script

Taylor Blau (2):
      blame-tree: use Bloom filters when available
      blame-tree: implement faster algorithm

Toon Claes (2):
      blame-tree: introduce new subcommand to blame files
      blame-tree.c: initialize revision machinery without walk

 .gitignore                 |   1 +
 Makefile                   |   2 +
 blame-tree.c               | 496 +++++++++++++++++++++++++++++++++++++++++++++
 blame-tree.h               |  30 +++
 builtin.h                  |   1 +
 builtin/blame-tree.c       |  43 ++++
 git.c                      |   1 +
 meson.build                |   2 +
 t/helper/test-tool.h       |   1 +
 t/meson.build              |   1 +
 t/perf/p8020-blame-tree.sh |  21 ++
 t/t8020-blame-tree.sh      | 148 ++++++++++++++
 12 files changed, 747 insertions(+)
---

---

base-commit: 4bbb303af69990ccd05fe3a2eb58a1ce036f8220 change-id: 20250410-toon-new-blame-tree-bcdbb78c1c0f

Thanks -- Toon