Use SM as a diff tool

[AmjadHD]

Problem description

Sometimes i wish i could use Sublime Merge as a diff tool to quickly compare two arbitrary files, much like git diff file1.txt file2.txt.

Preferred solution

Add a new command to smerge:
smerge diff file1.txt file2.txt
which, like git diff, can compare a tracked to untracked files.
Bindings can be made in ST to SM (e.g when the user selects two files from the sidebar or multi-selects two tabs,...)

[keith-hall]

related:
#434
#40

[michaelblyons]

I kind of feel like this is an exact dup of #40

[AmjadHD]

I did make a quick search but didn't make a thourough check.

[striatum]

This can be also achieved with:

smerge mergetool <FILE1> <FILE2>