git-clone-or-pull

#!/bin/sh

# git-clone-or-pull:  clone a GitHub repository, or pull it if already cloned.
#
# Usage: git-clone-or-pull ORG REPO_NAME [DESTINATION_PARENT] [GIT_CLONE_ARGS...]
#   ORG is the GitHub organization
#   REPO_NAME is the repository name (without the organization)
#   DESTINATION_PARENT is the directory that contains the clone directory.  It
#     defaults to the current directory.
#   GIT_CLONE_ARGS is extra arguments to git clone.  It defaults to
#     "-q --single-branch --depth 1" (without the quotes).
#     It is not used if the destination already exists.

SCRIPT_NAME="$(basename "$0")"

if [ "$#" -lt 2 ]; then
  echo "Usage: ${SCRIPT_NAME} ORG REPO_NAME [DESTINATION_PARENT] [GIT_CLONE_ARGS...]" >&2
  exit 1
fi

beginswith() { case $2 in "$1"*) true ;; *) false ;; esac }

ORG=$1
shift
REPO_NAME=$1
shift
DESTINATION_PARENT=.
if [ "$#" -ne 0 ]; then
  if ! beginswith "-" "$1"; then
    # Does not start with "-" and therefore isn't a command-line argument.
    DESTINATION_PARENT=$1
    shift
    if [ ! -d "${DESTINATION_PARENT}" ]; then
      mkdir -p "${DESTINATION_PARENT}"
    fi
  fi
fi
if [ "$#" -eq 0 ]; then
  # Default command-line arguments.
  set -- -q --single-branch --depth 1
fi

REPO_URL="https://github.com/${ORG}/${REPO_NAME}.git"
DESTINATION="${DESTINATION_PARENT:?}/${REPO_NAME}"

# Try twice in case of network lossage.  60 seconds is not enough to clone a branch of the JDK.
if test -d "${DESTINATION}"; then
  (cd "${DESTINATION}" && (timeout 180 git pull -q || (sleep 1m && (timeout 180 git pull || true))))
else
  if ! timeout 180 git clone "$@" "${REPO_URL}" "${DESTINATION}"; then
    rm -rf "${DESTINATION}"
    sleep 180
    if ! timeout 180 git clone "$@" "${REPO_URL}" "${DESTINATION}"; then
      echo "Failed to clone ${REPO_URL}"
      exit 1
    fi
  fi
fi

echo "${SCRIPT_NAME}: ${REPO_NAME} is at $(cd "${DESTINATION}" && git rev-parse HEAD)"