git checkout's reflog: even when detaching the HEAD, say from where

When checking out another ref, the reflogs already record from which
branch you switched.  Do that also when switching to a detached HEAD.

While at it, record also when coming _from_ a detached HEAD.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-checkout.sh b/git-checkout.sh
index f80939da5a15a006f2969cb966f4cdcc9dffdef9..f6d58ac044e5afb09855d687d3c1bcc8e2273be3 100755 (executable)
--- a/git-checkout.sh
+++ b/git-checkout.sh
@@ -266,7 +266,7 @@ if [ "$?" -eq 0 ]; then
        if test -n "$branch"
        then
                old_branch_name=`expr "z$oldbranch" : 'zrefs/heads/\(.*\)'`
-               GIT_DIR="$GIT_DIR" git symbolic-ref -m "checkout: moving from $old_branch_name to $branch" HEAD "refs/heads/$branch"
+               GIT_DIR="$GIT_DIR" git symbolic-ref -m "checkout: moving from ${old_branch_name:-$old} to $branch" HEAD "refs/heads/$branch"
                if test -n "$quiet"
                then
                        true    # nothing
@@ -278,7 +278,8 @@ if [ "$?" -eq 0 ]; then
                fi
        elif test -n "$detached"
        then
-               git update-ref --no-deref -m "checkout: moving to $arg" HEAD "$detached" ||
+               old_branch_name=`expr "z$oldbranch" : 'zrefs/heads/\(.*\)'`
+               git update-ref --no-deref -m "checkout: moving from ${old_branch_name:-$old} to $arg" HEAD "$detached" ||
                        die "Cannot detach HEAD"
                if test -n "$detach_warn"
                then