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

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

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

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
-- 
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