[FIX #2636] Add script for merging external contributions

Pulls, rebases, displays, signs and pushes external contributions.

If jq(1) and curl(1) are available, can pull data from GitHub and
mark PRs as closed, otherwise only code merging works.

Signed-off-by: Oskar Thoren <ot@oskarthoren.com>

scripts/merge-external-pr.sh

@@ -0,0 +1,152 @@
+#!/bin/bash
+
+set -eof pipefail
+
+trap cleanup EXIT
+
+fatal() {
+  echo "FATAL: $@" >&2
+  exit 1
+}
+
+warn() {
+  echo "$@"
+}
+
+confirm() {
+  read -p "$1 (type 'yes' to continue) " r
+  if [[ $r != yes ]]; then
+     exit 3
+  fi
+}
+
+load_config() {
+  [[ -f merge-external-pr.conf ]] && . merge-external-pr.conf
+  : ${OWNER:=status-im}
+  : ${REPO:=status-react}
+  : ${REMOTE:=origin}
+  : ${BRANCH:=develop}
+}
+
+check_pr_prereq() {
+  if ! command -v jq >/dev/null; then
+    fatal "jq(1) is not found, PR cannot be queried. Use REPO BRANCH"
+  fi
+  if ! command -v curl >/dev/null; then
+    fatal "curl(1) is not found, PR cannot be queried. Use REPO BRANCH"
+  fi
+}
+
+GH_URL_BASE="https://api.github.com"
+
+get_pr_info() {
+  echo '[ Reading PR info ]'
+  if [ $# -eq 1 ]; then
+    check_pr_prereq
+    local pr=$1
+    local pr_info_url="$GH_URL_BASE/repos/${OWNER}/${REPO}/pulls/$pr"
+    set +e
+    local pr_info
+    pr_info=$(curl -fsS "$pr_info_url")
+    if [ $? -ne 0 ]; then
+      fatal "Unable to get PR info from $pr_info_url"
+    fi
+    set -e
+    if [[ $(echo "$pr_info" | jq -r .state) == closed ]]; then
+      fatal "PR $pr is closed, will not merge"
+    fi
+    if [[ $(echo "$pr_info" | jq -r .maintainer_can_modify) == true ]]; then
+      RW_PR_REPO=1
+    else
+      warn "PR does not allow 'edits from maintainers', so it will be kept open"
+    fi
+    PR_URL=$(echo "$pr_info" | jq -r .head.repo.ssh_url)
+    PR_REMOTE_NAME=pr-$pr
+    PR_BRANCH=$(echo "$pr_info" | jq -r .head.ref)
+    PR_LOCAL_BRANCH=pr-$pr
+  else
+    PR_URL="$1"
+    PR_REMOTE_NAME=${PR_URL##*/}
+    PR_REMOTE_NAME=pr-${PR_REMOTE_NAME%.git}
+    PR_REMOTE_NAME=pr-${PR_REPO_NAME}
+    PR_BRANCH="$2"
+    PR_LOCAL_BRANCH=pr-${PR_REPO_NAME}
+  fi
+}
+
+fetch_pr() {
+  echo '[ Fetching PR ]'
+  git remote add $PR_REMOTE_NAME $PR_URL
+  git fetch $PR_REMOTE_NAME $PR_BRANCH
+}
+
+refresh_base_branch() {
+  git fetch $REMOTE $BRANCH
+}
+
+rebase_pr() {
+  git checkout -B $PR_LOCAL_BRANCH $PR_REMOTE_NAME/$PR_BRANCH
+  git rebase $BRANCH
+}
+
+check_is_pr_single_commit() {
+  if [[ $(git rev-list $BRANCH..$PR_LOCAL_BRACNCH | wc -l) -ne 1 ]] ;then
+    fatal "Only squashed/single-commit PRs can be merged"
+  fi
+}
+
+confirm_pr() {
+  git log -p $BRANCH..$PR_LOCAL_BRANCH
+  confirm "Do you like this PR?"
+}
+
+sign_pr() {
+  git commit --amend --gpg-sign --signoff
+}
+
+verify_pr() {
+  git show --show-signature $PR_LOCAL_BRANCH
+  confirm "Is the signature on the commit correct?"
+}
+
+merge_pr() {
+  # If PR is specified and can be pushed into, do it to mark PR as closed
+  if [[ -n $RW_PR_REPO ]]; then
+      git push -f $PR_REMOTE_NAME $PR_LOCAL_BRANCH:$PR_BRANCH
+  fi
+  git checkout $BRANCH
+  git merge --ff-only $PR_LOCAL_BRANCH
+  git push $REMOTE $BRANCH
+}
+
+cleanup() {
+  if [[ -z $DEBUG ]]; then
+      git checkout -q $BRANCH
+      git branch -q -D $PR_LOCAL_BRANCH 2>/dev/null || :
+      git remote remove $PR_REMOTE_NAME 2>/dev/null || :
+  fi
+}
+
+run() {
+  if [[ $# -lt 1 ]] || [[ $# -gt 2 ]]; then
+    cat <<EOF >&2
+Usage:
+  ./merge-external-pr.sh REPO_URL BRANCH
+  ./merge-external.pr.sh PR (if jq(1) and curl(1) are available)
+EOF
+    exit 2
+  fi
+  load_config
+  get_pr_info "$@"
+  cleanup
+  fetch_pr
+  refresh_base_branch
+  rebase_pr
+  check_is_pr_single_commit
+  confirm_pr
+  sign_pr
+  verify_pr
+  merge_pr
+}
+
+run "$@"