Comment button in file header is used for two different actions
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### Issue
The comment button in the file header is used for two different actions, depending on whether you're looking at a commit or an MR:
| Merge request | Commit |
| ------ | ------ |
|  |  |
### Proposal
- Add an ellipsis dropdown to the commit diffs
- Add `Toggle comments` and `View file` into ellipsis dropdown (to match MRs)
issue