[PATCH 0/3] midx: honor custom bases for incremental writes

[Taylor Blau <me@ttaylorr.com>]

SZEDER noticed[1] that t5334 was trying to call `nth_line()`, despite
that helper living only in t5335.

Fixing that should have made the test exercise `git multi-pack-index
write --incremental --base=...`. Instead, it uncovered another wrinkle,
which is that the normal MIDX write path parsed "--bases" without
actually passing it down to the MIDX writer.

This short series fixes both issues. It is structured as follows:

 * The first patch moves `nth_line()` to lib-midx.sh so that t5334 and
   t5335 use the same helper.

 * The second patch threads the parsed `--base` value through
   `write_midx_file()`, and consequently marks two t5334 cases as known
   breakages.

 * The final patch fixes the pack inclusion check and marks the tests
   successful again.

The result is that `--base=none` and `--base=<hash>` now correctly
produce detached incremental layers that include any packs above the
selected base, preserving reachability closure for bitmaps.

Thanks in advance for your review!

[1]: https://lore.kernel.org/git/aiuaf3fKJ6kIITrf@szeder.dev/

Taylor Blau (3):
  t5334: expose shared `nth_line()` helper
  midx: pass custom '--base' through incremental writes
  midx-write: include packs above custom incremental base

 builtin/multi-pack-index.c              |  3 ++-
 builtin/repack.c                        |  2 +-
 midx-write.c                            | 18 +++++++++++++-----
 midx.h                                  |  2 +-
 t/lib-midx.sh                           |  6 ++++++
 t/t5334-incremental-multi-pack-index.sh | 20 +++++++++++++++++---
 t/t5335-compact-multi-pack-index.sh     |  7 +------
 7 files changed, 41 insertions(+), 17 deletions(-)


base-commit: 3e65291872de10c3f0bf05ea8c24187e7a71ebf0
-- 
2.55.0.rc0.3.g7bf7c87b605