Allow use of tags in commit range comparison markdown references
Description
Currently, only commit hashes are allowed in commit range comparison markdown references. Example: gitlab-ce@21c2ffea5f50f9aa204d8ec6ba6b5cc47cba636e...b951e0d1
Proposal
Allow markdown references using tags to simplify version diffs. Example: v10.5.1...v10.5.2
The /compare
endpoint already supports this funcionality.