scm: backout r5213. do not display both 'View all revisions' and 'View revision'...

scm: backout r5213. do not display both 'View all revisions' and 'View revision' links (#7984, #7246).

Git and Mercurial support *branch*.

Git in repository root shows *master branch*.
Git master branch does not have all revisions.

Mercurial default branch is *default branch*.
Mercurial shows *tip* in repository root.

Mercurial does not treat directory. "hg log DIR" costs high.
Getting correct limited changesets in sub directory and branch is very heavy.
So, if there is no recent revision in sub directory and branch,
no changeset shows.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@5218 e93f8b46-1217-0410-a6f0-8f06a7374b81