Smaller, more reviewable chunks.
This is just one option, --arch. Future PRs may, if the reviewing
is easy, include multiple options. This one includes fixes to
the preprocessor script, though:
* big oops, I was not handling '<<something pod|something>>'
where 'pod' appears other than the beginning of the string.
* I was also not handling 'container<<| or pod>>', where one
side was empty.
* Behavior change: <<subcommand>>, on podman-pod-foo,
becomes just 'foo' (not 'pod foo'). This will be useful
in a future PR where we refactor --pod-id-file.
Signed-off-by: Ed Santiago <santiago@redhat.com>