context: rename divergent into contentdivergent
Rename divergent context method into contentdivergent and add a deprecation
warning on divergent.
Only update all callers to keep the patch straightforward.
The renaming is done according to
https://www.mercurial-scm.org/wiki/CEDVocabulary.
Differential Revision: https://phab.mercurial-scm.org/D240
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}