context: move handling of filtering error to revsymbol() (API)
When changectx's constructor runs into various Filtered*Error, it
creates an exception with a hint about using --hidden. This only makes
sense when the revision was provided by the user (if we get e.g. a
FilteredLookupError from repo[p1], then it's instead a programming
error). Thus, I'm moving the handling into revsymbol(). Also changed
"unfilteredrepo[changeid]" to "revsymbol(unfilteredrepo, changeid)" as
part of the move.
Differential Revision: https://phab.mercurial-scm.org/D3143
[workspace]
members = ["hgcli"]