topic: improve UX by using pager only when we should
Before this patch we were using pager in every case of topic command,
either it is setting up a new topic or clearing the active topic.
After this patch it will not use pager in following commands:
$ hg topic [TOPIC] -r [rev]
$ hg topic --clear
$ cat >> $HGRCPATH <<EOF
> [ui]
> logtemplate={rev}:{node|short}[{bookmarks}] ({obsolete}/{phase}) {desc|firstline}\n
> [extensions]
> EOF
$ echo "evolve=$(echo $(dirname $TESTDIR))/hgext3rd/evolve/" >> $HGRCPATH
$ mkcommit() {
> echo "$1" > "$1"
> hg add "$1"
> hg ci -m "add $1"
> }
$ hg init repo
$ cd repo
$ mkcommit a
$ mkcommit b
test disabling commands
$ cat >> .hg/hgrc <<EOF
> [experimental]
> evolution=createmarkers
> allowunstable
> exchange
> EOF
$ hg prune | head -n 2
hg: unknown command 'prune'
(use 'hg help' for a list of commands)