dispatch: pass around ui.fmsg channel
This will be set by the command server. See the next patch.
test-subrepo: document why share magically works even if subrepos are missing
I was confused how it's working while reviewing
fb490d798be0, "share: reload
repo after adjusting it in postshare()."
packaging: add Fedora 29 target
Differential Revision: https://phab.mercurial-scm.org/D5254