Git fails on mounted APFS file system

[dsl101]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

$ git --version --build-options

git version 2.41.0.windows.1
cpu: x86_64
built from commit: ff94e79c4724635915dbb3d4ba38f6bb91528260
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.19045.3086]

• What options did you set as part of the installation? Or did you choose the
  defaults?

# One of the following:
> type "C:\Program Files\Git\etc\install-options.txt"
> type "C:\Program Files (x86)\Git\etc\install-options.txt"
> type "%USERPROFILE%\AppData\Local\Programs\Git\etc\install-options.txt"
> type "$env:USERPROFILE\AppData\Local\Programs\Git\etc\install-options.txt"
$ cat /etc/install-options.txt

Editor Option: VIM
Custom Editor Path:
Default Branch Option:
Path Option: Cmd
SSH Option: OpenSSH
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFCommitAsIs
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Use Credential Manager: Enabled
Performance Tweaks FSCache: Enabled
Enable Symlinks: Disabled
Enable Pseudo Console Support: Disabled
Enable FSMonitor: Disabled

• Any other interesting things about your environment that might be related
  to the issue you're seeing?

Repository is in a mounted APFS file system, mapped as M:/

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

Windows Terminal running PowerShell 7.2.11

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

Edit a single file, then add—e.g.:

git add .\app.json

• What did you expect to occur after running these commands?

The file would be staged

• What actually happened instead?

Error: Rename from '.git/objects/31/tmp_obj_B1ugIR' to '.git/objects/31/f3444f8cb349e367661b6c6c659cd0934884fd' failed. Should I try again? (y/n)

I believe this is because git is creating its intermediate files 'read only', and that has the effect of setting the uchg flag on APFS, which then means the file can't be renamed or deleted. If I manually remove that flag, and then hit 'y' to the prompt, git will continue.

I haven't found any way to remove that uchg feature on the APFS side, or in the way the drive is mapped on the windows side.

[dscho]

Oh wow, that's an obscure use case ;-) Quite honestly, I have no viable idea how to address that from Git's side: Its assumption that it can create read-only files and then rename them once finished is pretty firm.

[dsl101]

Yes, I'm basically using the mac in order to run iOS simulator, but my main dev machine & tooling is all on windows and I couldn't face trying to setup & configure it all on the mac :).

I'm assuming there's implicit or explicit ordering there—create file, write contents, set to read only, rename. It would require reversing the last 2 I guess. But I don't know if that's done in one place or everywhere...

[dsl101]

Looks like somewhere around here is the shared code for this kind of thing. Perhaps something like this? (edited to only change attrs if necessary)

diff --git a/compat/mingw.c b/compat/mingw.c
index 274346e5c5..1d9f88fa38 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -2687,7 +2687,7 @@ int mingw_accept(int sockfd1, struct sockaddr *sa, socklen_t *sz)
 #undef rename
 int mingw_rename(const char *pold, const char *pnew)
 {
-	DWORD attrs = INVALID_FILE_ATTRIBUTES, gle;
+	DWORD attrs = INVALID_FILE_ATTRIBUTES, gle, attrsold;
 	int tries = 0;
 	wchar_t wpold[MAX_LONG_PATH], wpnew[MAX_LONG_PATH];
 	if (xutftowcs_long_path(wpold, pold) < 0 ||
@@ -2705,6 +2705,16 @@ int mingw_rename(const char *pold, const char *pnew)
 		if (CopyFileW(wpold, wpnew, FALSE) && !mingw_unlink(pold))
 			return 0;
 		gle = GetLastError();
+	} else if ((attrsold = GetFileAttributesW(wpold)) & FILE_ATTRIBUTE_READONLY) {
+		/* if file is read-only, change and retry */
+    SetFileAttributesW(wpold, attrsold & ~FILE_ATTRIBUTE_READONLY);
+		if (MoveFileExW(wpold, wpnew,
+				MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED)) {
+			/* reset attrs on renamed file */
+	    SetFileAttributesW(wpnew, attrsold);
+			return 0;
+		}
+		gle = GetLastError();
 	}
 
 	/* revert file attributes on failure */
@@ -2719,7 +2729,7 @@ int mingw_rename(const char *pold, const char *pnew)
 	if (attrs == INVALID_FILE_ATTRIBUTES &&
 	    (attrs = GetFileAttributesW(wpnew)) != INVALID_FILE_ATTRIBUTES) {
 		if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
-			DWORD attrsold = GetFileAttributesW(wpold);
+			attrsold = GetFileAttributesW(wpold);
 			if (attrsold == INVALID_FILE_ATTRIBUTES ||
 			    !(attrsold & FILE_ATTRIBUTE_DIRECTORY))
 				errno = EISDIR;

Unfortunately I don't think I have the wherewithal to build & test that, but would be happy to try it if someone can take a look.

[dsl101]

OK, well that was easier than I thought it would be. Downloaded the SDK and built, and my version now works as expected on APFS :). I'll submit a PR in case it's useful for others.