zsh_completion: handle --rev as well as -r for diff and revert
Completion for hg diff and revert should suggest all files in context of a
non-current revision. The script used to look only for `-r foo`, and now it
also understands `--rev foo`.
Differential Revision: https://phab.mercurial-scm.org/D4427
pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2
pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2