prompt: fix for simple rebase

When we are rebasing without options ('am' mode), the head rebased lives
in '$g/rebase-apply/head-name', so lets use that information so it's
reported the same way as if we were doing other rebases (-i or -m).

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-prompt.sh

@@ -279,6 +279,7 @@ __git_ps1 ()
 				step=$(cat "$g/rebase-apply/next")
 				total=$(cat "$g/rebase-apply/last")
 				if [ -f "$g/rebase-apply/rebasing" ]; then
+					b="$(cat "$g/rebase-apply/head-name")"
 					r="|REBASE"
 				elif [ -f "$g/rebase-apply/applying" ]; then
 					r="|AM"
@@ -295,6 +296,7 @@ __git_ps1 ()
 				r="|BISECTING"
 			fi
 
+			test -n "$b" ||
 			b="$(git symbolic-ref HEAD 2>/dev/null)" || {
 				detached=yes
 				b="$(

t/t9903-bash-prompt.sh

@@ -276,7 +276,7 @@ test_expect_success 'prompt - rebase merge' '
 '
 
 test_expect_success 'prompt - rebase' '
-	printf " ((t2)|REBASE 1/3)" > expected &&
+	printf " (b2|REBASE 1/3)" > expected &&
 	git checkout b2 &&
 	test_when_finished "git checkout master" &&
 	test_must_fail git rebase b1 b2 &&