[git] Unlink of file Failed. Should I try again?

You might see that error less often with Git 2.29 (Q4 2020): the "unlink" emulation on MinGW has been optimized.

See commit 680e0b4 (17 Aug 2020) by Jeff Hostetler (Jeff-Hostetler).
(Merged by Junio C Hamano -- gitster -- in commit 5a04826, 19 Aug 2020)

mingw: improve performance of mingw_unlink()

Signed-off-by: Jeff Hostetler
Signed-off-by: Johannes Schindelin

Update mingw_unlink() to first try to delete the file with existing permissions before trying to force it.

Windows throws an error when trying to delete a read-only file.
The mingw_unlink() compatibility wrapper always tries to _wchmod(666) the file before calling _wunlink() to avoid that error.
However, since most files in the worktree are already writable, this is usually wasted effort.

Update mingw_unlink() to just call DeleteFileW() directly and if that succeeds return.
If that fails, fall back into the existing code path to update the permissions and use _wunlink() to get the existing error code mapping.