[RFC PATCH v1 0/6] stash: drop usage of a second index

[Alban Gruin <alban.gruin@gmail.com>]

The old scripted `git stash' used to create a second index to save
modified and untracked files, and restore untracked files, without
affecting the main index.  This behaviour was carried on when it was
rewritten in C, and here, most operations performed on the second index
are done by forked commands (ie. `read-tree' instead of reset_tree(),
etc.).  This works most of the time, except in some edge case with the
split-index when the split file has expired and is deleted by a forked
command: the main index may still contain a reference to the now-deleted
file, and subsequent operations on the index will fail [0].

The goal of this series is to modernise (a bit) builtin/stash.c, and to
fix the aforementionned edge case.

I have to admit that I don't really know how to test this.
GIT_TEST_SPLIT_INDEX failed on me (gdb showed me that it does not enable
the split-index at all, at least in `git stash' and its forks), and I'm
reluctant to add explicits tests on `git stash' about the split-index,
when nothing in its code explicitly does unusual things with the index
once this series is applied.  If anyone wants to share opinions about
this, I would be happy to read them.

This series is based on b34789c0b0 ("The sixth batch", 2020-05-01).

The tip of this series is tagged as "stash-remove-second-index-v1" at
https://github.com/agrn/git.

[0] https://lore.kernel.org/git/EED2CFF1-5BEF-429D-AB99-AD148A867614@gmail.com/

Alban Gruin (6):
  stash: mark `i_tree' in reset_tree() const
  stash: remove the second index in stash_working_tree()
  stash: remove the second index in stash_patch()
  stash: remove the second index in save_untracked_files()
  stash: remove the second index in restore_untracked()
  stash: remove `stash_index_path'

 builtin/stash.c | 151 +++++++++++++++---------------------------------
 1 file changed, 46 insertions(+), 105 deletions(-)

-- 
2.26.2