Add git log viewer's features to commit viewer

The viewer for git logs has some convenient features which are missing from the viewer for a git commit, although both seem to display the same commit message:

• email addresses, Gerrit ids and Jira ids are clickable links
• right-clicking a commit id opens a context menu which allow various actions, e.g. "Check out <id>"

It would be nice if those features could be added to the commit viewer, too.