bug#20276: 24.4; diff-mode doesn't handle unified diff file headers without tabs

[Gustav Hållberg]

In diff-mode, "o" doesn't recognize unified diff file headers if they do

not contain tabs. Some diff programs will not emit tab + timestamp (as

GNU diff does), but just the file name.

Example working file header (where ".txt" is followed by tabs):

--- a.txt 2015-04-08 00:09:46.000000000 +0200

+++ b.txt 2015-04-08 00:09:51.000000000 +0200

Example failing file header:

--- a.txt

+++ b.txt

The fallback is for "o" to open the file on the leading "diff" line

which may or may not be present.

This used to work in Emacs 24.3.1 but does not as of the patch mentioned

here:

http://stackoverflow.com/questions/14720205/how-do-i-use-emacs-diff-with-spaces

My proposal is to fix this in (diff-hunk-file-names) by removing the

requirement for the trailing tab on the leading diff file header and

replace it with a no-newline check (sorry for not providing proper

patch):

-          (if (looking-at "[-*][-*][-*] \\([^\t]+\\)\t.*\n[-+][-+][-+] \\([^\t]+\\)")

+          (if (looking-at "[-*][-*][-*] \\([^\t\n]+\\).*\n[-+][-+][-+] \\([^\t\n]+\\)")

The return values should probably use (match-string-no-properties)

rather than (match-string) as well.

Thanks,

 Gustav