Re: [PATCH] refs: work around network caching on Windows

> On Fri, Jul 15, 2022 at 4:18 AM Johannes Schindelin via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> > Network shares sometimes use aggressive caching, in which case a
> > just-created directory might not be immediately visible to Git.
> >
> > One symptom of this scenario is the following error:
> >
> >         $ git tag -a -m "automatic tag creation"  test_dir/test_tag
> >         fatal: cannot lock ref 'refs/tags/test_dir/test_tag': unable to resolve reference 'refs/tags/test_dir/test_tag': Not a directory
> >
> > Note: This does not necessarily happen in all Windows setups. One setup
> > where it _did_ happen is a Windows Server 2019 VM, and as hinted in
> >
> >         http://woshub.com/slow-network-shared-folder-refresh-windows-server/
> >
> > the following commands worked around it:
> >
> >         Set-SmbClientConfiguration -DirectoryCacheLifetime 0
> >         Set-SmbClientConfiguration -FileInfoCacheLifetime 0
> >         Set-SmbClientConfiguration -FileNotFoundCacheLifetime 0
> >
> > This would impact performance negatively, though, as it essentially
> > turns off all caching, therefore we do not want to require users to do
> > that just to be able to use Git on Windows.
> >
> > The underlying culprit is that `GetFileAttributesExW()` that is called from
> > `mingw_lstat()` can raise an error `ERROR_PATH_NOT_FOUND`, which is
> > translated to `ENOTDIR`, as opposed to `ENOENT` as expected on Linux.
> >
> > Therefore, when trying to read a ref, let's allow `ENOTDIR` in addition
> > to `ENOENT` to indicate that said ref is missing.
> >
> > This fixes https://github.com/git-for-windows/git/issues/3727
> >
> > Signed-off-by: Pierre Garnier <pgarnier@mega.com>
> > Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> > ---
> > diff --git a/refs/files-backend.c b/refs/files-backend.c
> > @@ -381,7 +381,7 @@ stat_ref:
> > -               if (myerr != ENOENT || skip_packed_refs)
> > +               if ((myerr != ENOENT && myerr != ENOTDIR) || skip_packed_refs)
> > diff --git a/refs/packed-backend.c b/refs/packed-backend.c
> > @@ -480,7 +480,7 @@ static int load_contents(struct snapshot *snapshot)
> > -               if (errno == ENOENT) {
> > +               if (errno == ENOENT || errno == ENOTDIR) {
>
> The first question which popped into my mind upon reading the patch
> was why these changes need to be made to files-backend.c and
> packed-backend.c rather than "fixing" mingw_lstat() to return ENOENT
> instead of ENOTDIR.