Re: [PATCH] mingw: align symlinks-related rmdir() behavior with Linux

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

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Hi,

On Thu, 29 Jul 2021, Johannes Schindelin via GitGitGadget wrote:

> From: Johannes Schindelin <johannes.schindelin@gmx.de>

Sorry for missing this, this line should have read

	From: Thomas Bétous <tomspycell@gmail.com>

Ciao,
Dscho

>
> When performing a rebase, rmdir() is called on the folder .git/logs. On
> Unix rmdir() exits without deleting anything in case .git/logs is a
> symbolic link but the equivalent functions on Windows (_rmdir, _wrmdir
> and RemoveDirectoryW) do not behave the same and remove the folder if it
> is symlinked even if it is not empty.
>
> This creates issues when folders in .git/ are symlinks which is
> especially the case when git-repo[1] is used.
>
> This commit updates mingw_rmdir() so that its behavior is the same as
> Linux rmdir() in case of symbolic links.
>
> This fixes https://github.com/git-for-windows/git/issues/2967
>
> [1]: git-repo is a python tool built on top of Git which helps manage
> many Git repositories. It stores all the .git/ folders in a central
> place by taking advantage of symbolic links.
> More information: https://gerrit.googlesource.com/git-repo/
>
> Signed-off-by: Thomas Bétous <tomspycell@gmail.com>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>     mingw: support the git-repo tool better
>
>     This addresses an issue, originally reported at
>     https://github.com/git-for-windows/git/issues/2967, where the git-repo
>     tool [https://gerrit.googlesource.com/git-repo/] replaces folders in
>     .git/ with symlinks and mingw_rmdir() erroneously removes the symlink
>     target directory's contents.
>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1008%2Fdscho%2Ffix-rmdir-with-symlinks-on-windows-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1008/dscho/fix-rmdir-with-symlinks-on-windows-v1
> Pull-Request: https://github.com/gitgitgadget/git/pull/1008
>
>  compat/mingw.c    | 15 +++++++++++++++
>  t/t3400-rebase.sh | 10 ++++++++++
>  t/test-lib.sh     |  6 ++++++
>  3 files changed, 31 insertions(+)
>
> diff --git a/compat/mingw.c b/compat/mingw.c
> index aa647b367b0..685d3efa3c0 100644
> --- a/compat/mingw.c
> +++ b/compat/mingw.c
> @@ -341,6 +341,21 @@ int mingw_rmdir(const char *pathname)
>  {
>  	int ret, tries = 0;
>  	wchar_t wpathname[MAX_PATH];
> +	struct stat st;
> +
> +	/*
> +	* Contrary to Linux rmdir(), Windows' _wrmdir() and _rmdir()
> +	* will remove the directory at the path if it is a symbolic link
> +	* which leads to issues when symlinks are used in the .git folder
> +	* (in the context of git-repo for instance). So before calling _wrmdir()
> +	* we first check if the path is a symbolic link. If it is, we exit
> +	* and return the same error as Linux rmdir() in this case (ENOTDIR).
> +	*/
> +	if (!mingw_lstat(pathname, &st) && S_ISLNK(st.st_mode)) {
> +		errno = ENOTDIR;
> +		return -1;
> +	}
> +
>  	if (xutftowcs_path(wpathname, pathname) < 0)
>  		return -1;
>
> diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
> index 0bb88aa982b..23dbd3c82ed 100755
> --- a/t/t3400-rebase.sh
> +++ b/t/t3400-rebase.sh
> @@ -406,4 +406,14 @@ test_expect_success 'refuse to switch to branch checked out elsewhere' '
>  	test_i18ngrep "already checked out" err
>  '
>
> +test_expect_success MINGW,SYMLINKS_WINDOWS 'rebase when .git/logs is a symlink' '
> +	git checkout main &&
> +	mv .git/logs actual_logs &&
> +	cmd //c "mklink /D .git\logs ..\actual_logs" &&
> +	git rebase -f HEAD^ &&
> +	test -L .git/logs &&
> +	rm .git/logs &&
> +	mv actual_logs .git/logs
> +'
> +
>  test_done
> diff --git a/t/test-lib.sh b/t/test-lib.sh
> index adaf03543e8..73f6d645b66 100644
> --- a/t/test-lib.sh
> +++ b/t/test-lib.sh
> @@ -1513,6 +1513,12 @@ test_lazy_prereq SYMLINKS '
>  	ln -s x y && test -h y
>  '
>
> +test_lazy_prereq SYMLINKS_WINDOWS '
> +	# test whether symbolic links are enabled on Windows
> +	test_have_prereq MINGW &&
> +	cmd //c "mklink y x" &> /dev/null && test -h y
> +'
> +
>  test_lazy_prereq FILEMODE '
>  	test "$(git config --bool core.filemode)" = true
>  '
>
> base-commit: ebf3c04b262aa27fbb97f8a0156c2347fecafafb
> --
> gitgitgadget
>
>