Conflicts:
	doc/api/repositories.md

Change-Id: I7ebc39b47ff860813d9622ba6776583536e6e384

defaults to HEAD

Conflicts:
	spec/requests/api/repositories_spec.rb

Change-Id: Id114aca6c59d75f18e49bf9f33809a04e010bfb6

* dont allow protect/unprotect branches for users without master permissions
* dont allow access to Repository api for guests

Use "/commits/:sha/diff" as opposed to "/commit/:sha", keeping in line
with existing api urls (e.g. "/projects/:id", etc.)

Fix 500 error resulting from a diff api call with an invalid commit hash

Move "/commits/:sha/blob" to "/blobs/:sha", leaving the old path for
backwards compatibility.

Add ability to get a single commit via "/commits/:sha"