help: merge revsets.txt into revisions.txt
Selecting single and multiple revisions is closely related, so let's
put it in one place, so users can easily find it. We actually did not
even point to "hg help revsets" from "hg help revisions", but now that
they're on a single page, that won't be necessary.
.. Common link and substitution definitions.
.. |hg(1)| replace:: **hg**\ (1)
.. _hg(1): hg.1.html
.. |hgrc(5)| replace:: **hgrc**\ (5)
.. _hgrc(5): hgrc.5.html
.. |hgignore(5)| replace:: **hgignore**\ (5)
.. _hgignore(5): hgignore.5.html