completion: enhance "current branch" display

Introduce GIT_PS1_DESCRIBE option you can set to "contains", "branch", or
"describe" to tweak the way how a detached HEAD is described.

The default behaviour is to describe only exact match with some tag
(otherwise use the first 7 hexdigits) as before.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index be591468dbf9314f658721392c5a38a50a4fb6f9..dd6cd250e35cb695107d4a9f610752e09ec5bbb7 100755 (executable)
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -108,10 +108,21 @@ __git_ps1 ()
                        fi
 
                        b="$(git symbolic-ref HEAD 2>/dev/null)" || {
-                               b="$(git describe --exact-match HEAD 2>/dev/null)" ||
+
+                               b="$(
+                               case "${GIT_PS1_DESCRIBE_STYLE-}" in
+                               (contains)
+                                       git describe --contains HEAD ;;
+                               (branch)
+                                       git describe --contains --all HEAD ;;
+                               (describe)
+                                       git describe HEAD ;;
+                               (* | default)
+                                       git describe --exact-match HEAD ;;
+                               esac 2>/dev/null)" ||
+
                                b="$(cut -c1-7 "$g/HEAD" 2>/dev/null)..." ||
                                b="unknown"
-
                                b="($b)"
                        }
                fi