sharesafe: add functionality to automatically downgrade shares
Reasoning is same as previous patch which adds automatic upgrade support.
Downgrade is required as if automatic upgrade is enabled, all shares upgrade and
then source repository downgrades, shares won't work. We need to downgrade them.
Differential Revision: https://phab.mercurial-scm.org/D9680
#require docutils gettext
Error: the current ro localization has some rst defects exposed by
moving pager to core. These two warnings about references are expected
until the localization is corrected.
$ $TESTDIR/check-gendoc ro
checking for parse errors
gendoc.txt:58: (WARNING/2) Inline interpreted text or phrase reference start-string without end-string.
gendoc.txt:58: (WARNING/2) Inline interpreted text or phrase reference start-string without end-string.