submodule summary: do not fail before the first commit

diff --git a/git-submodule.sh b/git-submodule.sh
index 383dc451191fef4e078e9f46aaf3fdb3190ebc9a..9aa57dd6f7c939ec3d50386a039f1640ce2aa929 100755 (executable)
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -559,7 +559,8 @@ cmd_summary() {
                test $# = 0 || shift
        elif test -z "$1" -o "$1" = "HEAD"
        then
-               return
+               # before the first commit: compare with an empty tree
+               head=$(git hash-object -w -t tree --stdin </dev/null)
        else
                head="HEAD"
        fi