git-ps1.sh

# __git_ps1 accepts 0 or 1 arguments (i.e., format string)
# returns text to add to bash PS1 prompt (includes branch name)
__git_ps1 ()
{
	local g="$(git rev-parse --git-dir 2>/dev/null)"
	if [ -n "$g" ]; then
		local r
		local b
		if [ -d "$g/rebase-apply" ]
		then
			if test -f "$g/rebase-apply/rebasing"
			then
				r="|REBASE"
			elif test -f "$g/rebase-apply/applying"
			then
				r="|AM"
			else
				r="|AM/REBASE"
			fi
			b="$(git symbolic-ref HEAD 2>/dev/null)"
		elif [ -f "$g/rebase-merge/interactive" ]
		then
			r="|REBASE-i"
			b="$(cat "$g/rebase-merge/head-name")"
		elif [ -d "$g/rebase-merge" ]
		then
			r="|REBASE-m"
			b="$(cat "$g/rebase-merge/head-name")"
		elif [ -f "$g/MERGE_HEAD" ]
		then
			r="|MERGING"
			b="$(git symbolic-ref HEAD 2>/dev/null)"
		else
			if [ -f "$g/BISECT_LOG" ]
			then
				r="|BISECTING"
			fi
			if ! b="$(git symbolic-ref HEAD 2>/dev/null)"
			then
				if ! b="$(git describe --exact-match HEAD 2>/dev/null)"
				then
					b="$(cut -c1-7 "$g/HEAD")..."
				fi
			fi
		fi

		if [ -n "${1-}" ]; then
			printf "$1" "${b##refs/heads/}$r"
		else
			printf " (%s)" "${b##refs/heads/}$r"
		fi
	fi
}