tests/testlib/push-checkheads-util.sh

discovery: fix docstring of `outgoing` class

Also, introduce a more correct name `ancestorsof` for what was named
`missingheads` before. For now, we just forward `ancestorsof` to `missingheads`
until all users are changed.

There were some mistakes in the old docstring / name:

* `missingheads` (new name: `ancestorsof`) contains the revs whose ancestors
  are included in the outgoing operation. It may contain non-head revs and revs
  which are already on the remote, so the name "missingheads" is wrong in two
  ways.
* `missing` contains only ancestors of `missingheads`, so not *all nodes*
  present in local but not in remote.
* `common` might not contain all common revs, e.g. not some that are not an
  ancestor of `missingheads`.

It seems like the misleading name have fostered an actual bug (issue6372),
where `outgoing.missingheads` was used assuming that it contains the heads of
the missing changesets.

# setup config and various utility to test new heads checks on push

cat >> $HGRCPATH <<EOF
[ui]
# simpler log output
logtemplate ="{node|short} ({phase}): {desc}\n"

[phases]
# non publishing server
publish=False

[extensions]
# we need to strip some changeset for some test cases
strip=

[experimental]
# enable evolution
evolution=all

[alias]
# fix date used to create obsolete markers.
debugobsolete=debugobsolete -d '0 0'
EOF

mkcommit() {
   echo "$1" > "$1"
   hg add "$1"
   hg ci -m "$1"
}

getid() {
   hg log --hidden --template '{node}\n' --rev "$1"
}

setuprepos() {
    echo creating basic server and client repo
    hg init server
    cd server
    mkcommit root
    hg phase --public .
    mkcommit A0
    cd ..
    hg clone server client
}