Add add-ons/backport.sh script

add-ons/backport.sh

@@ -0,0 +1,148 @@
+#!/usr/bin/env bash
+# Open cherry-pick (backport) PRs for a merged PR, or clean up merged backport branches.
+#
+# Usage:
+#   add-ons/backport.sh [-r owner/repo] [-R remote] [-n] <pr|url> [branch...]
+#   add-ons/backport.sh [-r owner/repo] [-R remote] [-n] --cleanup
+#
+# Without branches, targets the highest numeric version branch (e.g. 2.14).
+# Branch names are pick-<pr>-<target>; each PR gets the "backport" label.
+# Uses gh if available, otherwise git + curl with $GITHUB_TOKEN (or $GH_TOKEN).
+
+set -euo pipefail
+
+REPO=cvmfs/doc-cvmfs
+REMOTE=origin
+LABEL=backport
+DRY=
+CLEANUP=
+
+die() { echo "error: $*" >&2; exit 1; }
+run() { if [ -n "$DRY" ]; then echo "+ $*"; else "$@"; fi; }
+# Help text is the header comment block, up to the first non-comment line.
+usage() { awk 'NR > 1 && !/^#/ { exit } NR > 1 { sub(/^# ?/, ""); print }' "$0"; exit "${1:-0}"; }
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    -r|--repo) REPO=$2; shift 2 ;;
+    -R|--remote) REMOTE=$2; shift 2 ;;
+    -n|--dry-run) DRY=1; shift ;;
+    --cleanup) CLEANUP=1; shift ;;
+    -h|--help) usage ;;
+    -*) die "unknown option $1" ;;
+    *) break ;;
+  esac
+done
+
+if command -v gh >/dev/null && gh auth status >/dev/null 2>&1; then
+  USE_GH=1
+else
+  USE_GH=
+  TOKEN=${GITHUB_TOKEN:-${GH_TOKEN:-}}
+  [ -n "$TOKEN" ] || die "need an authenticated gh or GITHUB_TOKEN"
+  command -v jq >/dev/null || die "fallback mode needs jq"
+fi
+
+api() {  # api METHOD PATH [JSON]
+  curl -fsS -X "$1" -H "Authorization: Bearer $TOKEN" \
+    -H "Accept: application/vnd.github+json" \
+    ${3:+-d "$3"} "https://api.github.com/repos/$REPO/$2"
+}
+
+# Prints "merged" if the branch's PR was merged, nothing otherwise.
+pr_merged_for_branch() {
+  local owner=${REPO%%/*}
+  if [ -n "$USE_GH" ]; then
+    gh pr list -R "$REPO" --head "$1" --state merged --json number -q 'if length > 0 then "merged" else empty end'
+  else
+    api GET "pulls?state=closed&head=$owner:$1" | jq -r 'if any(.[]; .merged_at != null) then "merged" else empty end'
+  fi
+}
+
+if [ -n "$CLEANUP" ]; then
+  git fetch --prune "$REMOTE"
+  current=$(git branch --show-current)
+  for b in $(git for-each-ref --format='%(refname:short)' 'refs/heads/pick-*'); do
+    [ "$(pr_merged_for_branch "$b")" = merged ] || continue
+    [ "$b" = "$current" ] && { echo "skip $b (checked out)"; continue; }
+    run git branch -D "$b"
+    if git show-ref -q --verify "refs/remotes/$REMOTE/$b"; then
+      run git push "$REMOTE" --delete "$b"
+    fi
+  done
+  exit 0
+fi
+
+[ $# -ge 1 ] || usage 1
+PR=$1; shift
+if [[ $PR =~ github\.com/([^/]+/[^/]+)/pull/([0-9]+) ]]; then
+  REPO=${BASH_REMATCH[1]}
+  PR=${BASH_REMATCH[2]}
+fi
+[[ $PR =~ ^[0-9]+$ ]] || die "not a PR number or URL: $PR"
+TARGETS=("$@")
+
+git fetch "$REMOTE"
+if [ ${#TARGETS[@]} -eq 0 ]; then
+  latest=$(git for-each-ref --format='%(refname:lstrip=3)' "refs/remotes/$REMOTE/" |
+    grep -E '^[0-9]+\.[0-9]+$' | sort -t. -k1,1n -k2,2n | tail -1)
+  [ -n "$latest" ] || die "no version branch found on $REMOTE"
+  TARGETS=("$latest")
+fi
+
+if [ -n "$USE_GH" ]; then
+  read -r TITLE < <(gh pr view "$PR" -R "$REPO" --json title -q .title)
+  SHA=$(gh pr view "$PR" -R "$REPO" --json mergeCommit -q '.mergeCommit.oid // empty')
+  NCOMMITS=$(gh pr view "$PR" -R "$REPO" --json commits -q '.commits | length')
+else
+  json=$(api GET "pulls/$PR")
+  TITLE=$(jq -r .title <<<"$json")
+  SHA=$(jq -r '.merge_commit_sha // empty' <<<"$json")
+  NCOMMITS=$(jq -r .commits <<<"$json")
+  [ "$(jq -r .merged <<<"$json")" = true ] || SHA=
+fi
+[ -n "$SHA" ] || die "PR #$PR is not merged"
+git cat-file -e "$SHA" 2>/dev/null || git fetch "$REMOTE" "$SHA"
+
+patch_id() { git show "$1" | git patch-id --stable | cut -d' ' -f1; }
+
+# The merge commit is the whole PR for a merge or squash merge, but only the
+# last commit for a rebase merge. A rebase merge is recognized by the merge
+# commit having the same patch as the PR head.
+if [ "$(git rev-list --parents -n1 "$SHA" | wc -w)" -gt 2 ]; then
+  pick=(-m 1 "$SHA")
+elif [ "$NCOMMITS" -gt 1 ] && git fetch -q "$REMOTE" "refs/pull/$PR/head" &&
+     [ "$(patch_id "$SHA")" = "$(patch_id FETCH_HEAD)" ]; then
+  pick=("$SHA~$NCOMMITS..$SHA")
+else
+  pick=("$SHA")
+fi
+
+start=$(git branch --show-current)
+for tgt in "${TARGETS[@]}"; do
+  branch="pick-$PR-$tgt"
+  echo "== #$PR -> $tgt ($branch)"
+  git show-ref -q --verify "refs/remotes/$REMOTE/$tgt" || die "no branch $REMOTE/$tgt"
+  run git switch -c "$branch" "$REMOTE/$tgt"
+  if ! run git cherry-pick -x "${pick[@]}"; then
+    echo "Cherry-pick conflict on $branch. Resolve, 'git cherry-pick --continue'," >&2
+    echo "then rerun with the remaining branches." >&2
+    exit 1
+  fi
+  run git push -u "$REMOTE" "$branch"
+  title="$TITLE ($tgt)"
+  body="Cherry-pick #$PR to $tgt"
+  if [ -n "$USE_GH" ]; then
+    run gh pr create -R "$REPO" --base "$tgt" --head "$branch" \
+      --title "$title" --body "$body" --label "$LABEL"
+  else
+    payload=$(jq -n --arg t "$title" --arg b "$body" --arg base "$tgt" --arg h "$branch" \
+      '{title:$t, body:$b, base:$base, head:$h}')
+    if [ -n "$DRY" ]; then echo "+ POST pulls $payload"; else
+      num=$(api POST pulls "$payload" | jq -r .number)
+      api POST "issues/$num/labels" "{\"labels\":[\"$LABEL\"]}" >/dev/null
+      echo "https://github.com/$REPO/pull/$num"
+    fi
+  fi
+done
+[ -n "$start" ] && run git switch "$start"