[PATCHv3 05/16] bash prompt: print unique detached HEAD abbreviated object name

["SZEDER Gábor" <szeder@ira.uka.de>]

When describing a detached HEAD according to the $GIT_PS1_DESCRIBE
environment variable fails, __git_ps1() runs 'cut -c1-7 .git/HEAD' to
show the 7 hexdigits abbreviated commit object name in the prompt.
Obviously, this neither respects core.abbrev nor produces a unique
object name.

Fix this by using 'git rev-parse --short HEAD' instead and adjust the
corresponding test to use non-standard number of hexdigits.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
---
 contrib/completion/git-prompt.sh | 2 +-
 t/t9903-bash-prompt.sh           | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/contrib/completion/git-prompt.sh b/contrib/completion/git-prompt.sh
index 07a6218d..3c5e62bb 100644
--- a/contrib/completion/git-prompt.sh
+++ b/contrib/completion/git-prompt.sh
@@ -392,7 +392,7 @@ __git_ps1 ()
 					git describe --tags --exact-match HEAD ;;
 				esac 2>/dev/null)" ||
 
-				b="$(cut -c1-7 "$g/HEAD" 2>/dev/null)..." ||
+				b="$(git rev-parse --short HEAD 2>/dev/null)..." ||
 				b="unknown"
 				b="($b)"
 			}
diff --git a/t/t9903-bash-prompt.sh b/t/t9903-bash-prompt.sh
index 416e6219..0d53aa6d 100755
--- a/t/t9903-bash-prompt.sh
+++ b/t/t9903-bash-prompt.sh
@@ -50,7 +50,8 @@ test_expect_success SYMLINKS 'prompt - branch name - symlink symref' '
 '
 
 test_expect_success 'prompt - detached head' '
-	printf " ((%s...))" $(git log -1 --format="%h" b1^) >expected &&
+	printf " ((%s...))" $(git log -1 --format="%h" --abbrev=13 b1^) >expected &&
+	test_config core.abbrev 13 &&
 	git checkout b1^ &&
 	test_when_finished "git checkout master" &&
 	__git_ps1 >"$actual" &&
-- 
1.8.3.1.599.g4459181