Summary:
Fixes T7938.
- Primarily, users can currently shoot themselves in the foot by putting `../../etc/passwd` and other similar nonsense in these fields (this is not dangerous, but also does not work). Require sensible names.
- Enforce uniqueness so these names can be used in URIs and as identifiers in the future.
- (This doesn't start actually using them for anything fancy yet.)
Test Plan:
- Gave several repositories clone names: a valid name, two duplicate names, an invalid, name, some with no names.
- Ran migrations.
- Got clean conversion for valid names, appropriate errors for invalid/duplicate names.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T7938
Differential Revision: https://secure.phabricator.com/D14986
