Implement option --vcs to force use of certain VCS

[0mp]

This is useful if you've got a Git repository nested within a Subversion repository and you wish to see the diff as seen by svn instead of git.

[ymattw]

Thank you for your PR and truly sorry I could not respond earlier.

Reading your reason again, I unfortunately could not accept this patch just for the race use case you mentioned. Over time I learned a lesson, I regretted I accepted the major feature-add of reading diffs from version control, I should have kept it as simple as possible - just read diff from stdin.

Your case have easy workarounds:

• run git diff or svn diff respectively and pipe into ydiff, or
• cd to subdir and run ydiff

I hope this makes sense to you. Thanks again for your interests.

[0mp]

I absolutely understand. Have a great day!

PS Thanks a lot for maintaining ydiff! :)