git/{diff,import}: make it easier to handle manually-asembled patch emails

git/{diff,import}: make it easier to handle manually-asembled patch emails
Often, people (including myself) will write emails that
can almost be applied with git/import.  This changes
git/diff and git/import so that things will generally
work even when assembling diffs by hand:

1.	git/import becomes slightly more lax:

		^diff ...
		^--- ...

	will both be detected as the start of a patch.

2.  git/diff produces the same format of diff
	as git/export, starting with paths:

		--- a/path/to/file
		+++	b/path/to/file

	which means that the 'ape/patch -p1' used
	within git/import will just work.

So with this, if you send an email to the mailing list,
write up a committable description, and append the
output of git/diff to the end of the email, git/import
should just work.

[this patch was send through the mailing list using the
above procedure, and will be committed with git/import
to verify that it works as advertised]