#!/bin/bash

set -euox pipefail

unset GREP_OPTIONS

compatbranches=$(hg branches --quiet | grep 'mercurial-' | grep -v ':' | sort -n --reverse)

prev='stable'

topic=${1:-'test-compat'}

for branch in $compatbranches; do

    # Logic in the revsets below:

    # 1. There is target topic on stable or compatibility branch: merge all

    # those commits, they are related to our work and need to pass tests on all

    # compatibility branches.

    # 2. There is no target topic: avoid any commits that have topic set, they

    # are definitely unrelated to what we're doing.

    # In other words, if you want to test certain commits, assign them all to

    # one topic and provide that topic as the first argument to this script.

    uptarget="first(max(branch('$branch') and topic('$topic')) or max(branch('$branch') and not topic()))"

    hg up -r "$uptarget"

    hg topic "$topic"

    mergetarget="first(max(branch('$prev') and topic('$topic')) or max(branch('$prev') and not topic()))"

    hg merge -r "$mergetarget"

    hg commit -m "test-compat: merge $prev into $branch"

    prev=$branch

done