Convert bazaar repos from lp directory into git repos in gh directory

migrate-bzr-to-git.sh

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

# Migrates Bazaar branches in ./lp/<name> to bare Git repos in ./gh/<name>.git
# If ./lp/<name> is missing (or not a bzr branch), it will "brz branch lp:<name> ./lp/<name>".
#
# Optional env:
#   DEFAULT_BRANCH=main   # rename 'master' to 'main' and set HEAD accordingly
#   ONLY=<comma,separated,names>  # process only these names (matching subdirs or Launchpad names)

require() { command -v "$1" >/dev/null 2>&1 || { echo "Missing: $1" >&2; exit 1; }; }
require brz
require git

ROOT="${PWD}"
LP_DIR="${ROOT}/lp"
GH_DIR="${ROOT}/gh"
CACHE_DIR="${ROOT}/.cache-bzr2git"

mkdir -p "$LP_DIR" "$GH_DIR" "$CACHE_DIR"

# Expand list of projects
declare -a names=()
if [[ -n "${ONLY:-}" ]]; then
  IFS=',' read -r -a names <<<"$ONLY"
else
  while IFS= read -r -d '' path; do
    base="$(basename "$path")"
    names+=("$base")
  done < <(find "$LP_DIR" -mindepth 1 -maxdepth 1 -type d -print0 | sort -z)
fi

if [[ "${#names[@]}" -eq 0 ]]; then
  echo "No projects found under $LP_DIR and no ONLY=… given." >&2
  exit 1
fi

for name in "${names[@]}"; do
  echo "────────────────────────────────────────────────────────────"
  echo "Project: $name"

  BZR_DIR="${LP_DIR}/${name}"
  GIT_DIR="${GH_DIR}/${name}.git"
  BZR_MARKS="${CACHE_DIR}/${name}.bzr.marks"
  GIT_MARKS="${CACHE_DIR}/${name}.git.marks"

  # 1) Ensure we have a local Bazaar branch; if not, try Launchpad.
  if [[ ! -d "${BZR_DIR}/.bzr" ]]; then
    echo "No .bzr in ${BZR_DIR}; attempting: brz branch lp:${name} ${BZR_DIR}"
    mkdir -p "$LP_DIR"
    brz branch "lp:${name}" "${BZR_DIR}"
  fi

  # Quick sanity info
  echo "Bazaar info:"
  (cd "${BZR_DIR}" && brz info | sed 's/^/  /')

  # 2) Prepare bare git target
  if [[ ! -d "${GIT_DIR}" ]]; then
    echo "Initializing bare git repo: ${GIT_DIR}"
    git init --bare "${GIT_DIR}" >/dev/null
  fi

  # 3) Stream Bazaar → Git with per-project marks (idempotent & re-runnable)
  echo "Importing history (this may take a moment)…"
  # Create marks files if missing to let fast-import update them
  : > "${BZR_MARKS}" || true
  : > "${GIT_MARKS}" || true

  # Export + import in one pipe
  brz fast-export --export-marks="${BZR_MARKS}" "${BZR_DIR}" \
    | git --git-dir="${GIT_DIR}" fast-import --export-marks="${GIT_MARKS}"

  # 4) Optional: rename default branch (e.g., master → main) and set HEAD
  if [[ -n "${DEFAULT_BRANCH:-}" ]]; then
    echo "Setting default branch to '${DEFAULT_BRANCH}' (renaming if needed)…"
    # Try to rename master → DEFAULT_BRANCH if master exists
    if git --git-dir="${GIT_DIR}" show-ref --verify --quiet refs/heads/master; then
      if [[ "${DEFAULT_BRANCH}" != "master" ]]; then
        git --git-dir="${GIT_DIR}" branch -m master "${DEFAULT_BRANCH}" || true
      fi
    fi
    # Ensure HEAD points at DEFAULT_BRANCH (create it if importer used a different name)
    if git --git-dir="${GIT_DIR}" show-ref --verify --quiet "refs/heads/${DEFAULT_BRANCH}"; then
      git --git-dir="${GIT_DIR}" symbolic-ref HEAD "refs/heads/${DEFAULT_BRANCH}"
    fi
  fi

  # 5) Report refs
  echo "Heads:"
  git --git-dir="${GIT_DIR}" for-each-ref --format='  %(refname:short)' refs/heads/ | sort || true
  echo "Tags:"
  git --git-dir="${GIT_DIR}" for-each-ref --format='  %(refname:short)' refs/tags/ | sort || true

  echo "Done: ${GIT_DIR}"
done

echo "All done. Bare Git repos are in: ${GH_DIR}"
echo "Tip: to inspect one repo, run: git clone ./gh/<name>.git"