Thu, 6 Jul 2023 23:36:30 +0200

mingw: optionally enable wsl compability file mode bits

The Windows Subsystem for Linux (WSL) version 2 allows to use `chmod` on
NTFS volumes provided that they are mounted with metadata enabled (see
https://devblogs.microsoft.com/commandline/chmod-chown-wsl-improvements/
for details), for example:

	$ chmod 0755 /mnt/d/test/a.sh

In order to facilitate better collaboration between the Windows
version of Git and the WSL version of Git, we can make the Windows
version of Git also support reading and writing NTFS file modes
in a manner compatible with WSL.

Since this slightly slows down operations where lots of files are
created (such as an initial checkout), this feature is only enabled when
`core.WSLCompat` is set to true. Note that you also have to set
`core.fileMode=true` in repositories that have been initialized without
enabling WSL compatibility.

There are several ways to enable metadata loading for NTFS volumes
in WSL, one of which is to modify `/etc/wsl.conf` by adding:

```
[automount]
enabled = true
options = "metadata,umask=027,fmask=117"
```

And reboot WSL.

It can also be enabled temporarily by this incantation:

	$ sudo umount /mnt/c &&
	  sudo mount -t drvfs C: /mnt/c -o metadata,uid=1000,gid=1000,umask=22,fmask=111

It's important to note that this modification is compatible with, but
does not depend on WSL. The helper functions in this commit can operate
independently and functions normally on devices where WSL is not
installed or properly configured.

Signed-off-by: xungeng li <[email protected]>
Signed-off-by: Johannes Schindelin <[email protected]>