scmutil: move revsingle/pair/range from cmdutil
This allows users at levels below the command layer to avoid import loops.
help: consolidate topic hooks in help.py
This removes loops like cmdutil->revset->help->extensions->cmdutil and
simplifies the code.
extensions: drop maxlength from enabled and disabled
This is a bad/silly API. Instead calculate maxlength in one place in help
it's used and simplify all the callers.
hgcia: Handle URL like in notify (
issue2406)
The URL must be composed with baseurl and webroot like in notify