Files can have an RSS feed, but those only make sense when taken in the
context of a branch. There is no history to make a feed of on a tag or a
commit: they're static. Forgejo does not provide a feed for them for
this reason.
However, the file view on the web UI was offering a link to these
non-existent feeds. With this patch, it does that no longer, and only
provides a link when viewing the file in the context of a branch.
Fixes#2102.
Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
4b48d21ea7