scmutil: use resolvehexnodeidprefix() from revsymbol()
I should have copied this from changectx.__init__ into in
35b34202dd3b
(context: handle partial nodeids in revsymbol(), 2018-04-08).
Differential Revision: https://phab.mercurial-scm.org/D3310
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}