Merge request discussion feed does not state merge request version

Problem to solve

When browsing through the discussion feed, new commits/versions are reported with a list of commit shas and a comparison link.

But the version of the MR that this creates is not shown. If you are trying to review changes since you last reviewed, this makes it very hard to find the version to select in the merge request changes tab. This is made worse by the fact that the version selector does not show commit messages, only versions.

Discussion tab	Merge request versions

Further details

Use cases:

• Reviewing changes since you last reviewed
• Identifying the number of versions of the MR easily

Proposal

In the Discussion tab in Merge Requests, the merge request version should be stated explicitly in the discussion thread.

Additionally, we should take the opportunity to improve push activity by:

• adding a link to compare with the latest version
• making the push notification more compact

Links / references

Vaguely related to https://gitlab.com/gitlab-org/gitlab-ce/issues/26723