name: Go lint
description: >
  Run golangci-lint with the shared configuration, or the repository's own
  .golangci.yml when it has one, reporting only issues in the code a push or
  pull request changed.

inputs:
  version:
    description: golangci-lint version, installed when the runner has a different one
    default: 2.15.0
  config:
    description: Configuration file; empty uses the repository's .golangci.yml, else the shared one
    default: ''
  new_from_rev:
    description: >
      Report issues only after this revision. auto: the pushed range, or the merge
      base with the pull request's target; empty: report everything.
    default: auto
  working_directory:
    description: Directory of the Go module
    default: .
  args:
    description: Extra golangci-lint arguments
    default: ''

runs:
  using: composite
  steps:
    - name: Lint
      shell: bash
      working-directory: ${{ inputs.working_directory }}
      env:
        VERSION: ${{ inputs.version }}
        CONFIG: ${{ inputs.config }}
        NEW_FROM_REV: ${{ inputs.new_from_rev }}
        ARGS: ${{ inputs.args }}
        SHARED_CONFIG: ${{ github.action_path }}/golangci.yml
        EVENT: ${{ github.event_name }}
        BEFORE: ${{ github.event.before }}
        BASE_REF: ${{ github.base_ref }}
        DEFAULT_BRANCH: ${{ github.event.repository.default_branch }}
      run: |
        set -euo pipefail
        lint=golangci-lint
        if ! command -v golangci-lint >/dev/null || [[ "$(golangci-lint version --short 2>/dev/null)" != "$VERSION" ]]; then
          curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/HEAD/install.sh | sh -s -- -b "$RUNNER_TEMP/golangci" "v$VERSION"
          lint="$RUNNER_TEMP/golangci/golangci-lint"
        fi

        if [ -z "$CONFIG" ]; then
          CONFIG=$(ls .golangci.yml .golangci.yaml 2>/dev/null | head -1 || true)
          CONFIG=${CONFIG:-$SHARED_CONFIG}
        fi
        echo "config: $CONFIG"

        # The checkout is usually shallow, and a shallow history has no base to compare against.
        [ "$(git rev-parse --is-shallow-repository)" = true ] && git fetch -q --unshallow
        new=()
        if [ "$NEW_FROM_REV" = auto ]; then
          if [ "$EVENT" = pull_request ] && [ -n "$BASE_REF" ]; then
            git fetch -q origin "$BASE_REF"
            new=(--new-from-merge-base="origin/$BASE_REF")
          elif [ -n "$BEFORE" ] && [[ ! "$BEFORE" =~ ^0+$ ]] && git cat-file -e "$BEFORE^{commit}" 2>/dev/null; then
            new=(--new-from-rev="$BEFORE")
          else
            # A new branch or a manual run: what the branch adds to the default branch.
            git fetch -q origin "${DEFAULT_BRANCH:-master}"
            new=(--new-from-merge-base="origin/${DEFAULT_BRANCH:-master}")
          fi
        elif [ -n "$NEW_FROM_REV" ]; then
          new=(--new-from-rev="$NEW_FROM_REV")
        fi
        echo "reporting: ${new[*]:-everything}"

        # shellcheck disable=SC2086
        "$lint" run --config "$CONFIG" "${new[@]}" $ARGS