help: revise explanation about capability check while selecting merge tool
This is follow up of
7c6044634957 and
cded904f7acc.
This patch adds explanations about:
- notation in capability columns in the table
- how capabilities of external merge tools are treated
Issue351: mq: qrefresh can create extra revlog entry
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ echo b > b
$ hg ci -A -m foo
adding b
$ echo cc > b
$ hg qnew -f foo.diff
$ echo b > b
$ hg qrefresh
$ hg debugindex b
rev linkrev nodeid p1 p2
0 0 1e88685f5dde 000000000000 000000000000