Re: [PATCH] clean: demonstrate a bug with pathspecs

[Elijah Newren <newren@gmail.com>]

On Wed, Jan 15, 2020 at 12:25 PM Derrick Stolee via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> 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(+)
>
> diff --git a/t/t7300-clean.sh b/t/t7300-clean.sh
> index 6e6d24c1c3..782e125c89 100755
> --- a/t/t7300-clean.sh
> +++ b/t/t7300-clean.sh
> @@ -737,4 +737,13 @@ test_expect_success MINGW 'handle clean & core.longpaths = false nicely' '
>         test_i18ngrep "too long" .git/err
>  '
>
> +test_expect_failure 'clean untracked paths by pathspec' '
> +       git init untracked &&
> +       mkdir untracked/dir &&
> +       echo >untracked/dir/file.txt &&
> +       git -C untracked clean -f dir/file.txt &&
> +       ls untracked/dir >actual &&
> +       test_must_be_empty actual
> +'
> +
>  test_done
>
> base-commit: b9670c1f5e6b98837c489a03ac0d343d30e08505
> --
> gitgitgadget

Is there an inverted phrase corresponding to "the gift that keeps on
giving", something like "the punishment that keeps on punishing"?  If
so, it would be a very appropriate description of dir.c.

Yeah, I still have context.  I even think I've got an idea about what
the fix might be, though with dir.c my ideas about fixes usually just
serve as starting points for debugging before I find the real fix.
I'll try to dig in.