tests/test-revlog-group-emptyiter.t

hgweb: add a "URL breadcrumb" to the index and repository pages

The purpose of this change is to make it much easier to navigate up the
repository tree when the hg web server is used to serve more than one
repository.

A "URL breadcrumb" is a path where each of the path items can be clicked to go
to the corresponding path page.

This lets you go up the folder hierarchy very quickly. For example, when showing
the list of repositories in http://myserver/myteams/myprojects, the following
"breadcrumb" will be shown:

Mercurial > myteams > myprojects

Clicking on "myprojects" reloads the page. Clicking on "myteams" goes up one
folder. Clicking on the leftmost "Mercurial" goes to the server root.

This "breadcrumb" also appears on all repository pages. For example on the
summary page of the repository at http://myserver/myteams/myprojects/myrepo the
following will be shown:

Mercurial > myteams > myprojects > myrepo / summary

This change has been applied to all templates that already had a link to the
main repository page (i.e. gitweb, monoblue, paper and coal) plus to the index
page of the spartan template.

In order to make the breadcumb links stand out the some of the template styles
have been customized.

Issue1678: IndexError when pushing

setting up base repo
  $ hg init a
  $ cd a
  $ touch a
  $ hg ci -Am a
  adding a
  $ cd ..

cloning base repo
  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd b

setting up cset to push
  $ hg up null
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ touch a
different msg so we get a clog new entry
  $ hg ci -Am b
  adding a
  created new head

pushing
  $ hg push -f ../a
  pushing to ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)

  $ cd ..