branch-or-tag

#!/usr/bin/env bash
usage() {
  echo -n "branch-or-tag [OPTION]... [FILE]...

Prints the branch or tag of a git repository.

  -t, --type    Print the git reference type ('branch' or 'tag').

If PWD is tracking a branch, print "branch".
If PWD is in a DETACHED HEAD state, and there is a tag for the SHA, print "tag".
If the PWD is in a DETACHED HEAD state, and there is no tag, exit with an error.
"
}

BRANCH=`git symbolic-ref --quiet --short HEAD 2> /dev/null`
TAG=`git describe --tags --exact-match 2> /dev/null`

# Set up options for --type and --help.
while [ $# -gt 0 ]; do
  case "$1" in
    -t|--type)
        if [[ -n $BRANCH ]]; then
          echo "branch"
        elif [[ -n $TAG ]]; then
          echo "tag"
        else
          exit 1
        fi

        exit 0
      ;;
    -h|--help) usage >&2; exit 0;;
    *)
      echo "Invalid option: $1"
      exit 1
  esac
  shift
done

# Print the branch or tag name
if [[ -n $BRANCH ]]; then
  echo $BRANCH
elif [[ -n $TAG ]]; then
  echo $TAG
else
  exit 1
fi