Add diff syntax definition

[uranusjr]

Largely based on git’s definition for inserted and deleted, but expanded to support

1. All coord styles including diff -c and diff -u.
2. The >/< syntax.
3. The ! syntax in context diff.

Example page included.

For the ! syntax I aliased important to diff.

[TimothyGu]

In general, +1, although I would appreciate it if you can make Git depend on diff instead of still being stand-alone.

[uranusjr]

I don’t own the Git syntax though. Would be happy to help if @lgiraudel thinks this is a good idea.

[LeaVerou]

Why escape the angle brackets? Also + doesn’t need escaping inside a character class.
Also, what’s the negative lookahead trying to prevent? What happens if the line starts with e.g. ++ or >>?

[LeaVerou]

Overall looks nice, see a few minor comments.
Thanks for adding examples too!
Please fix the merge conflicts?

Re:git, once I merge this, feel free to submit a PR to make it dependent on diff. It makes sense. Just because you don’t own it doesn’t mean you can’t suggest changes to it!

[uranusjr]

Thanks @LeaVerou, amended. Sorry for the changes taking so long, I totally forgot about this. :(

[Golmote]

(You should not have included the autohotkey changes in this PR)
Thanks, I'm merging.

[Golmote]

@uranusjr Is it intended that those two lines in unified diff are matched as "coord"?

--- qcli.yml    2014-12-16 11:43:41.000000000 +0800
+++ /Users/uranusjr/Desktop/qcli.yml    2014-12-31 11:28:08.000000000 +0800

EDIT: The separator --- in normal diff is also matched as coord.

[uranusjr]

@Golmote Yes that is what I intended, since they sort of act as separators between diff chunks, like the *** lines in context diff. That’s just my opinion though; I wouldn’t mind if you want it be done differently.

[Golmote]

I'm telling because of #401 and #769. I just modified the git component to match those lines as "inserted" and "deleted".
I'll try to think of a way to distinguish between those lines containing file names and the lines containing coords.