Re: [PATCH 2/5] add: allow operating on a sparse-only index

On 7/21/21 6:19 PM, Junio C Hamano wrote:

"Derrick Stolee via GitGitGadget" [off-list ref] writes:

quoted

From: Derrick Stolee <redacted>

Disable command_requires_full_index for 'git add'. This does not require
any additional removals of ensure_full_index(). The main reason is that
'git add' discovers changes based on the pathspec and the worktree
itself. These are then inserted into the index directly, and calls to
index_name_pos() or index_file_exists() already call expand_to_path() at
the appropriate time to support a sparse-index.

OK.  With that explained, it still is quite surprising that we only
need this change (eh, rather, doing this change is safe without
doing anything else).

Yes, all of the hard work was done by the earlier work to expand
a sparse index when we search for a specific path that lands
within a sparse directory. See 95e0321 (read-cache: expand on query
into sparse-directory entry, 2021-04-01) for the specifics.

quoted

-	# This "git add folder1/a" fails with a warning
-	# in the sparse repos, differing from the full
-	# repo. This is intentional.
-	test_sparse_match test_must_fail git add folder1/a &&
-	test_sparse_match test_must_fail git add --refresh folder1/a &&
-	test_all_match git status --porcelain=v2 &&

And nice to see a known limitation lifted.

Thank you for pointing this out. This actually starts to _fail_ now
that we allow sparse indexes in 'git add', but it's because the error
messages don't match, not that the 'test_must_fail' is violated.

Patch 4 adds a similar test that is then set to work in patch 5. That
allows us a clear way to describe the behavior change and to motivate
the fix in patch 5. This could be explained better, perhaps by merging
Patch 4 into this one. That helps describe how this specific case
changes behavior (for the worse) in this patch, but is handled in a
careful way later, once the behavior change is documented.

If there is a better way to reorganize these patches, then I could
try another approach.

Thanks,
-Stolee