@matheusbsbs / matheus-bagliano / commits / 3e7d4888e5

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

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: It replaces `.git/logs/` with a symlink. One such issue is that the _target_ of that symlink is removed e.g. during a `git rebase`, where `delete_reflog("REBASE_HEAD")` will not only try to remove `.git/logs/REBASE_HEAD` but then recursively try to remove the parent directories until an error occurs, a technique that obviously relies on `rmdir()` refusing to remove a symlink. This was reported in https://github.com/git-for-windows/git/issues/2967. This commit updates mingw_rmdir() so that its behavior is the same as Linux rmdir() in case of symbolic links. To verify that Git does not regress on the reported issue, this patch adds a regression test for the `git rebase` symptom, even if the same `rmdir()` behavior is quite likely to cause potential problems in other Git commands as well. [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> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Thomas Bétous committed Aug 2, 2021 at 21:07 UTC 3e7d4888e5b83f1ed75667ff557b8996f427adf0
3 files changed +37
compat/mingw.c
+21
@@ -341,6 +341,27 @@ int mingw_rmdir(const char *pathname)
341 {
342 int ret, tries = 0;
343 wchar_t wpathname[MAX_PATH];
344 + struct stat st;
345 +
346 + /*
347 + * Contrary to Linux' `rmdir()`, Windows' _wrmdir() and _rmdir()
348 + * (and `RemoveDirectoryW()`) will attempt to remove the target of a
349 + * symbolic link (if it points to a directory).
350 + *
351 + * This behavior breaks the assumption of e.g. `remove_path()` which
352 + * upon successful deletion of a file will attempt to remove its parent
353 + * directories recursively until failure (which usually happens when
354 + * the directory is not empty).
355 + *
356 + * Therefore, before calling `_wrmdir()`, we first check if the path is
357 + * a symbolic link. If it is, we exit and return the same error as
358 + * Linux' `rmdir()` would, i.e. `ENOTDIR`.
359 + */
360 + if (!mingw_lstat(pathname, &st) && S_ISLNK(st.st_mode)) {
361 + errno = ENOTDIR;
362 + return -1;
363 + }
364 +
365 if (xutftowcs_path(wpathname, pathname) < 0)
366 return -1;
367
t/t3400-rebase.sh
+10
@@ -406,4 +406,14 @@ test_expect_success 'refuse to switch to branch checked out elsewhere' '
406 test_i18ngrep "already checked out" err
407 '
408
409 +test_expect_success MINGW,SYMLINKS_WINDOWS 'rebase when .git/logs is a symlink' '
410 + git checkout main &&
411 + mv .git/logs actual_logs &&
412 + cmd //c "mklink /D .git\logs ..\actual_logs" &&
413 + git rebase -f HEAD^ &&
414 + test -L .git/logs &&
415 + rm .git/logs &&
416 + mv actual_logs .git/logs
417 +'
418 +
419 test_done
t/test-lib.sh
+6
@@ -1513,6 +1513,12 @@ test_lazy_prereq SYMLINKS '
1513 ln -s x y && test -h y
1514 '
1515
1516 +test_lazy_prereq SYMLINKS_WINDOWS '
1517 + # test whether symbolic links are enabled on Windows
1518 + test_have_prereq MINGW &&
1519 + cmd //c "mklink y x" &> /dev/null && test -h y
1520 +'
1521 +
1522 test_lazy_prereq FILEMODE '
1523 test "$(git config --bool core.filemode)" = true
1524 '