-#!/bin/sh
+#!/usr/bin/env bash
set -eu
set -o pipefail
-gitdir="$1"
-fallback="$2"
+dir="$1"
+tag="$2"
+fallback="$3"
-git --git-dir="$gitdir" describe --abbrev=7 --dirty=+ 2>/dev/null | sed 's/^v//' || echo "$fallback"
+if [ -n "$tag" ]; then
+ echo "$tag"
+ exit 0
+fi
+
+# Apparently git describe has a bug where it always considers the work-tree
+# dirty when invoked with --git-dir (even though 'git status' is happy). Work
+# around this issue by cd-ing to the source directory.
+cd "$dir"
+# Check that we have either .git/ (a normal clone) or a .git file (a work-tree)
+# and that we don't get confused if a tarball is extracted in a higher-level
+# git repository.
+[ -e .git ] && git describe --abbrev=7 --dirty=+ 2>/dev/null | sed 's/^v//' || echo "$fallback"