[BUG] diff algorithm selection issue

Hi all,

When the config has diff.algorithm=patience set, "git diff --minimal" seems to
be ignored, and does not give the same output as "git diff --diff-algorithm=minimal",
but really the same as "git diff --diff-algorithm=patience".

See top commit on https://gitlab.com/ydirson/omaha/-/commits/bug/git-diff-minimal
where patience diff manages to show a quite braindead diff.

Also, I found it curious that in the manpage the long (--diff-algorithm=minimal) and
short (--minimal) forms are described with a copy-paste of the text, and no mention
of them being equivalent (or not, for that matter ;).