#!/usr/bin/env bash

# This script implements a two-way mirroring bewteen a GH wiki for a repo `R`
# (called `DOTREMOTE` below) with a public repo `R-wiki` (intended for external
# contributions, called `DASHREMOTE` below).  See `sync.yml` for how it is
# triggered: it is a minimal-ish yaml file that should be added to both sides
# (`R` and `R-wiki`), with a `push` trigger on `R-wiki` (and optionally a
# schedule) and a `gollum` trigger on `R`.  The action spec is careful to
# always checkout `R-wiki` (`DASHREMOTE`) since checking out `R` would be
# useless.  It then merges in changes in `DOTREMOTE` and pushes the results to
# both.  Pushing the merged version will trigger an action on the other side,
# but that would be very quick (both the `merge` and pushing it will be
# no-ops.)

set -ue
shopt -s extglob

PUSHER="${PUSHER// +( )/ }"; PUSHER="${PUSHER# }"; PUSHER="${PUSHER% }"
NAME="${PUSHER% <*}"
EMAIL="${PUSHER##* <}"; EMAIL="${EMAIL%>}"
echo "Setting git username to \"$NAME\" and email to \"$EMAIL\""
export GIT_AUTHOR_NAME="$NAME"
export GIT_AUTHOR_EMAIL="$EMAIL"
export GIT_COMMITTER_NAME="$NAME"
export GIT_COMMITTER_EMAIL="$EMAIL"

DASHREMOTE="$(git remote get-url origin)"
DOTREMOTE="${DASHREMOTE//-wiki/.wiki}"
echo "DASHREMOTE = $DASHREMOTE, DOTREMOTE = $DOTREMOTE"

for r in "$DASHREMOTE" "$DOTREMOTE"; do
  if [[ "$(git ls-remote --symref "$r" HEAD | grep "^ref:")" \
          != $'ref: refs/heads/master\tHEAD' ]]; then
    echo "Unexpected branch name at $r: expected to see \"master\""
  fi
done

echo ">>> Adding and fetching DOTREMOTE"
git remote add dot "$DOTREMOTE"
git fetch dot

echo ">>> Merging changes"
git pull --no-edit --no-rebase dot "master"

echo ">>> Pushing merges to DASHREMOTE"
git push origin

echo ">>> Pushing merges to DOTREMOTE"
git push dot main:master