log: use revsetlang.formatspec() thoroughly
This patch replaces %(val)s and %(val)r with %r (expression) and %s (string)
respectively. _matchfiles() is the exception as it takes a list of string
parameters.
"--prune REV" could take a revset expression if it were "ancestors(%(val)s)",
but this patch doesn't change the existing behavior.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}