Get permalink for specific line number
Permalinks are very useful. If you link to a file in `master` the contents can change very quickly making the link meaningless. We should make it easy to get a permalink for a specific line number.
### Proposal
- Add a button near the line numbers to get a permalink for that line
### Links / references
https://gitlab.com/gitlab-org/gitlab-ce/issues/50024#note_94279364
issue