makefile: add $ to environment variables in help message
templater: selecting a style with no templates does not crash (issue4140)

Running `hg log --style compact` (or any other style) raised a traceback when
no template directory was there. Now there is a message:

Abort: style 'compact' not found
(available styles: no templates found, try `hg debuginstall` for more info)


There is no test because this would require to rename the template directory.
But this would influence other tests running in parallel. And when the test
would be aborted the wrong named directory would remain, especially a problem
when running with -l.
hgext: fix one typo in rebase
phase: properly compute ancestors of --rev on push (issue3786)

Now that discovery is working on unfiltered changeset, I had a good occasion to
look at that bug again. This let me realise that a trivial node vs rev
comparision was the cause of this two years old bugs…

Happy second birthday phases!
wix: pull in new templates
parsers: fix 'unsigned expression is always true' warning (issue4142)

On Mac OS gcc-llvm throws an -Wtautological-compare warning because flen
is defined as an unsigned integer, therefore flen < 0 is always true.
subrepo: do not try to get hidden revisions

If a subrepo revision is hidden (because it was amended, for example) it does
not make sense to try to "get" it from the remote subrepository.

Note that in order to avoid making the change look bigger than it is, this adds
an unnecessary else clause. This will be removed on a follow up patch.
subrepo: remove unnecessary else clause in hgsubrepo._get

This revision has no behaviour change. It simply removes an unnecessary else
that follows an if / return block. The change looks big because a big chunk of
code has been unindented one level.
subrepo: make it possible to update to hidden subrepo revisions

When a subrepo revision was hidden it was considered missing and mercurial was
unable to update to the corresponding parent revision. Instead warn the user of
the problem and let it choose what to do (the default is to udpate anyway).