generate-delete-accepted-mr-branches.sh

#!/usr/bin/env bash
set -euo pipefail

PROJECT_PATH="${PROJECT_PATH:-ghc/ghc}"
AUTHOR_USERNAME="${AUTHOR_USERNAME:-TerrorJack}"
ACCEPTED_ASSIGNEE_USERNAME="${ACCEPTED_ASSIGNEE_USERNAME:-marge-bot}"
GLAB_HOST="${GLAB_HOST:-gitlab.haskell.org}"
DELETE_REMOTE="${DELETE_REMOTE:-origin}"

require_command() {
  local command_name=$1

  if ! command -v "$command_name" >/dev/null 2>&1; then
    printf 'error: required command not found: %s\n' "$command_name" >&2
    exit 1
  fi
}

urlencode() {
  jq -nr --arg value "$1" '$value | @uri'
}

fetch_merge_requests() {
  local query=$1

  glab api "${glab_api_flags[@]}" \
    "projects/${project_path}/merge_requests?${query}&per_page=100" \
    --paginate \
    --output ndjson
}

list_local_remote_branches() {
  local remote_ref_prefix="refs/remotes/${DELETE_REMOTE}/"

  git for-each-ref --format='%(refname)' "$remote_ref_prefix" \
    | jq -R --arg prefix "$remote_ref_prefix" '
        select(startswith($prefix))
        | .[($prefix | length):]
        | select(. != "HEAD")
      ' \
    | jq -s 'unique | sort'
}

require_command glab
require_command git
require_command jq

local_remote_branches_file=$(mktemp)
trap 'rm -f "$local_remote_branches_file"' EXIT

project_path=$(urlencode "$PROJECT_PATH")
author_username=${AUTHOR_USERNAME#@}
accepted_assignee_username=${ACCEPTED_ASSIGNEE_USERNAME#@}
author_username_query=$(urlencode "$author_username")
accepted_assignee_username_query=$(urlencode "$accepted_assignee_username")

glab_api_flags=(--hostname "$GLAB_HOST")

accepted_merge_requests_json=$(
  {
    fetch_merge_requests \
      "state=merged&author_username=${author_username_query}"
    fetch_merge_requests \
      "state=closed&author_username=${author_username_query}&assignee_username=${accepted_assignee_username_query}"
  } | jq -s \
    --arg accepted_assignee_username "$accepted_assignee_username" \
    '
      map(
        select(
          .state == "merged"
          or (
            .state == "closed"
            and any(.assignees[]?; .username == $accepted_assignee_username)
          )
        )
      )
      | unique_by(.id)
      | map(select(.source_branch != null and .source_branch != ""))
      | sort_by(.iid)
    '
)

accepted_merge_request_count=$(jq 'length' <<<"$accepted_merge_requests_json")
list_local_remote_branches >"$local_remote_branches_file"

same_project_accepted_merge_requests_json=$(
  jq '
    map(
      select(
        .source_project_id != null
        and .target_project_id != null
        and .source_project_id == .target_project_id
        and .source_branch != null
        and .source_branch != ""
        and .source_branch != .target_branch
      )
    )
  ' <<<"$accepted_merge_requests_json"
)

same_project_accepted_merge_request_count=$(jq 'length' <<<"$same_project_accepted_merge_requests_json")

accepted_merge_requests_with_local_ref_json=$(
  jq \
    --slurpfile local_remote_branches "$local_remote_branches_file" \
    '
      map(
        select(
          .source_branch as $source_branch
          | $local_remote_branches[0]
          | index($source_branch)
        )
      )
      | sort_by(.source_branch, .iid)
    ' <<<"$same_project_accepted_merge_requests_json"
)

accepted_merge_requests_with_local_ref_count=$(jq 'length' <<<"$accepted_merge_requests_with_local_ref_json")

delete_branches_json=$(
  jq '
    group_by(.source_branch)
    | map({
        source_branch: .[0].source_branch,
        merge_requests: map({
          iid,
          title,
          web_url,
          reference: (.references.full // ("!" + (.iid | tostring))),
          short_reference: (.references.short // ("!" + (.iid | tostring)))
        })
      })
    | sort_by(.source_branch)
  ' <<<"$accepted_merge_requests_with_local_ref_json"
)

delete_branch_count=$(jq 'length' <<<"$delete_branches_json")
quoted_delete_remote=$(jq -nr --arg value "$DELETE_REMOTE" '$value | @sh')

cat <<SCRIPT
#!/usr/bin/env bash
set -euo pipefail

# Generated by $(basename "$0") on $(date -u +'%Y-%m-%dT%H:%M:%SZ').
# Accepted merge requests found: ${accepted_merge_request_count}
# Same-project accepted merge requests: ${same_project_accepted_merge_request_count}
# Same-project accepted merge requests with local refs/remotes/${DELETE_REMOTE}/ refs: ${accepted_merge_requests_with_local_ref_count}
# Unique remote branches emitted: ${delete_branch_count}
# Source query:
#   host: ${GLAB_HOST}
#   project: ${PROJECT_PATH}
#   author: @${author_username}
#   accepted when state=merged, or state=closed and assignee=@${accepted_assignee_username}
#   emitted only when source_project_id == target_project_id
#   emitted only when the branch exists locally under refs/remotes/${DELETE_REMOTE}/

default_remote=${quoted_delete_remote}
remote="\${REMOTE:-\$default_remote}"

delete_branch() {
  local branch=\$1
  local refs=\$2
  local remote_ref="refs/remotes/\${remote}/\${branch}"

  if git show-ref --verify --quiet "\$remote_ref"; then
    printf 'Deleting %s for %s from %s\n' "\$branch" "\$refs" "\$remote" >&2
    git push "\$remote" --delete "\$branch"
  else
    printf 'Skipping %s for %s: local remote ref not found: %s\n' "\$branch" "\$refs" "\$remote_ref" >&2
  fi
}

SCRIPT

jq -r '
  def clean_comment:
    tostring | gsub("[\r\n]+"; " ");

  .[]
  | .merge_requests as $merge_requests
  | ($merge_requests | map(.short_reference) | join(", ")) as $short_references
  | ($merge_requests | map(.reference) | join(", ")) as $references
  | "# " + $references
    + if ($merge_requests | length) == 1 then
        ": " + ($merge_requests[0].title | clean_comment)
      else
        ": " + (($merge_requests | length) | tostring) + " accepted merge requests share this source branch"
      end
    + "\n" + ($merge_requests | map("# " + .web_url) | join("\n"))
    + "\ndelete_branch "
    + (.source_branch | @sh)
    + " "
    + ($short_references | @sh)
    + "\n"
' <<<"$delete_branches_json"