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!

--HG--
branch : stable
wix: pull in new templates

--HG--
branch : stable
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.

--HG--
branch : stable