devel/git: Fix 'git maintenance start'

Add a patch from upstream to fix 'git maintenance start'. Here follow
upstream commit message:

While cron is specified by POSIX, there are a wide variety of
implementations in use. On FreeBSD, the cron implementation requires a
file name argument: if the user wants to edit standard input, they must
specify "-". However, this notation is not specified by POSIX, allowing
the possibility that making such a change may break other, less common
implementations.

Since POSIX tells us that cron must accept a file name argument, let's
solve this problem by specifying a temporary file instead. This will
ensure that we work with the vast majority of implementations.

Note that because delete_tempfile closes the file for us, we should not
call fclose here on the handle, since doing so will introduce a double
free.

PR: 260746
Reported by: Mark Waite <mark.earl.waite@gmail.com>
Obtained from: https://lore.kernel.org/git/1dd29f43-1a8e-eb69-3320-7f5140a0e18e@github.com/T/#me47087c1f9034c82da8eae83db18cc6114c2c1e5
Sponsored by: Rubicon Communications, LLC ("Netgate")