Scan for vcs repos and save, ignore feature, `add-from-fs`

[tony]

Allow scanning for repos with a find/ag.

$ vcspull scan [path]  # prompt to merge into config (creating backup first) or create new

Should allow ignore dirs/patterns. Be fast, leverage https://github.com/ggreer/the_silver_searcher if in PATH.

[pirhoo]

This would be awesome! In the meantime, I made this:
https://gist.github.com/pirhoo/9f1f42ed73c929e1e19101356482daeb

[tony]

Actually - rather than write a python script, plan to add command to /home/d/work/python/vcspull that can:

• Feature request: command to add new repository #333: add (can be ran in various ways, e.g. vcspull add my-repo to add my-repo, or vcspull add my-repo <url> to add ./my-repo with repo of `, or have a dir passed to it via flag
• this: add-from-fs (scans for git repos and adds them to current manifest)