[PATCH] clean: demonstrate a bug with pathspecs

From: Derrick Stolee <dstolee@microsoft.com>

b9660c1 (dir: fix checks on common prefix directory, 2019-12-19) modified the way pathspecs are handled when handling a directory during "git clean -f <path>". While this improved the behavior for known test breakages, it also regressed in how the clean command handles cleaning a specified file.

Add a test case that demonstrates this behavior. This test passes before b9660c1 then fails after.

Helped-by: Kevin Willford <Kevin.Willford@microsoft.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
    clean: demonstrate a bug with pathspecs
    
    While integrating v2.25.0 into the microsoft/git fork, one of our VFS
    for Git functional tests started failing. Looking into it, the only
    possible place could have been where one of our integration points with
    the virtualfilesystem hook was moved by c5c4edd (dir: break part of
    read_directory_recursive() out for reuse, 2019-12-10) and then used in
    the following two commits.
    
    By reverting these two commits, we stopped the failure, but it took a
    while before figuring out that it was a regression in Git and not a
    failure in our integration to the new logic. Thanks to Kevin Willford
    for producing a test case.
    
    b9660c1 (dir: fix checks on common prefix directory, 2019-12-19) is the
    culprit, so this patch is based on that. If rebased to c5c4edd, then the
    test passes.
    
    As for actually fixing this regression, I don't know how. This code is
    pretty dense and I don't have a firm grasp of what is happening in both
    b9660c1 and the following 777b420 (dir: synchronize tread_leading_path()
    and read_directory_recursive()). Elijah is CC'd in case he still has
    context on this area.
    
    Thanks, -Stolee

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-526%2Fderrickstolee%2Fclean-bug-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-526/derrickstolee/clean-bug-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/526

 t/t7300-clean.sh | 9 +++++++++
 1 file changed, 9 insertions(+)