#!/usr/bin/env bash
# Print the ref a build is named after: <branch>-<sha12>, plus -dirty when
# the tree has uncommitted changes. Slashes and anything else awkward in a
# docker tag or S3 prefix become dashes; a detached HEAD contributes no
# branch. Callers may set BUILD_REF instead, so a push computes the ref once
# and hands it to the build it runs.
set -euo pipefail

ref=$(git rev-parse --short=12 HEAD)
branch=$(git rev-parse --abbrev-ref HEAD)
if [ "$branch" != HEAD ]; then
  ref="$(printf '%s' "$branch" | tr -c 'A-Za-z0-9_.-' '-')-$ref"
fi
if [ -n "$(git status --porcelain)" ]; then
  ref="$ref-dirty"
  echo "working tree is dirty; ref is $ref" >&2
fi
printf '%s\n' "$ref"