#!/bin/bash

#

# produces two repositories with different common and missing subsets

#

#   $ discovery-helper.sh REPO NBHEADS DEPT

#

# The Goal is to produce two repositories with some common part and some

# exclusive part on each side. Provide a source repository REPO, it will

# produce two repositories REPO-left and REPO-right.

#

# Each repository will be missing some revisions exclusive to NBHEADS of the

# repo topological heads. These heads and revisions exclusive to them (up to

# DEPTH depth) are stripped.

#

# The "left" repository will use the NBHEADS first heads (sorted by

# description). The "right" use the last NBHEADS one.

#

# To find out how many topological heads a repo has, use:

#

#   $ hg heads -t -T '{rev}\n' | wc -l

#

# Example:

#

#  The `pypy-2018-09-01` repository has 192 heads. To produce two repositories

#  with 92 common heads and ~50 exclusive heads on each side.

#

#    $ ./discovery-helper.sh pypy-2018-08-01 50 10

set -euo pipefail

printusage () {

     echo "usage: `basename $0` REPO NBHEADS DEPTH [left|right]" >&2

}

if [ $# -lt 3 ]; then

    printusage

    exit 64

fi

repo="$1"

shift

nbheads="$1"

shift

depth="$1"

shift

doleft=1

doright=1

if [ $# -gt 1 ]; then

    printusage

    exit 64

elif [ $# -eq 1 ]; then

    if [ "$1" == "left" ]; then

        doleft=1

        doright=0

    elif [ "$1" == "right" ]; then

        doleft=0

        doright=1

    else

        printusage

        exit 64

    fi

fi

leftrepo="${repo}-${nbheads}h-${depth}d-left"

rightrepo="${repo}-${nbheads}h-${depth}d-right"

left="first(sort(heads(all()), 'desc'), $nbheads)"

right="last(sort(heads(all()), 'desc'), $nbheads)"

leftsubset="ancestors($left, $depth) and only($left, heads(all() - $left))"

rightsubset="ancestors($right, $depth) and only($right, heads(all() - $right))"

echo '### creating left/right repositories with missing changesets:'

if [ $doleft -eq 1 ]; then

    echo '# left  revset:' '"'${leftsubset}'"'

fi

if [ $doright -eq 1 ]; then

    echo '# right revset:' '"'${rightsubset}'"'

fi

buildone() {

    side="$1"

    dest="$2"

    revset="$3"

    echo "### building $side repository: $dest"

    if [ -e "$dest" ]; then

        echo "destination repo already exists: $dest" >&2

        exit 1

    fi

    echo '# cloning'

    if ! cp --recursive --reflink=always ${repo} ${dest}; then

        hg clone --noupdate "${repo}" "${dest}"

    fi

    echo '# stripping' '"'${revset}'"'

    hg -R "${dest}" --config extensions.strip= strip --rev "$revset" --no-backup

}

if [ $doleft -eq 1 ]; then

    buildone left "$leftrepo" "$leftsubset"

fi

if [ $doright -eq 1 ]; then

    buildone right "$rightrepo" "$rightsubset"

fi