Add missing History link to directory listings (#4829)
The feature to list commits from a subdirectory is already there but
so far the history link to it was missing. There is a History button
in the view_file.tmpl already so avoid showing two history buttons in
that case.
The GitHub webinterface has the same History button in the same place
so this makes gitea a little bit more compatible.
Signed-off-by: Bernhard Froehlich <decke@bluelife.at>