bug#26028: 26.0.50; epatch for multifile patches

[Tino Calancha <tino.calancha@gmail.com>]

On Wed, 24 May 2017, Michael Heerdegen wrote:

> Tino Calancha <tino.calancha@gmail.com> writes:
>
>> Recently i am not using `epatch', but maybe following patch
>> is of interest for someone:
>
> FWIW, do you think you understood all of the code you changed (I ask
> because I gave up after a while)?
I think so.  I you exclude from the patch the added tests in
test/lisp/vc/ediff-ptch-tests.el
then this patch just touch:
2 files changed, 42 insertions(+), 18 deletions(-)
The only it does:
* tweak the original heuristic part for guessing the file names
* change the suggested defaults in the prompts asking for the patch and
   dirs to patch.

>  If you did, do you think we should
> install your fix, or are there open questions?
I have tested with plain diffs and with Git diffs.  I didn't test it
with other VC than Git.
I don't think solves all the problems, but at least it makes 
`epatch' usable for the most common multipatch situations.

I)
You know, `epatch' has never parsed multipatches with files in different 
dirs, as:
foo/file1
bar/file2

II)
The only multipatches `epatch' worked before is when all the files belong
to the same dir, as:
foo/file1
foo/file2

This patch makes possible to handle I) as well.