Add interactive mode for hide/unhide

[mfulbright]

Adding an interactive mode for hiding or unhiding commits, similar to how switch works, would be useful. The use cases for hide/unhide and switch are similar - they all need to identify 1+ commits, so a similar interaction for doing so seems to make sense.

Proposed command:

$ git hide -i
<interactive commit picker launches>
$ git unhide -i
<interactive commit picker launches>