submodule: no [--merge|--rebase] when newly cloned

"git submodule update" can be run with either the "--merge" or "--rebase"
option, or submodule.<name>.update configuration variable can be set to
"merge" or "rebase, to cause local work to get integrated when updating
the submodule.

When a submodule is newly cloned, however, it does not have a check out
when a rebase or merge is attempted, leading to a failure.  For newly
cloned submodules, simply check out the appropriate revision.  There is no
local work to integrate with for them.

Signed-off-by: Spencer E. Olson <olsonse@umich.edu>
Acked-by: Jens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -423,6 +423,7 @@ cmd_update()
 		cmd_init "--" "$@" || return
 	fi
 
+	cloned_modules=
 	module_list "$@" |
 	while read mode sha1 stage path
 	do
@@ -442,6 +443,7 @@ cmd_update()
 		if ! test -d "$path"/.git -o -f "$path"/.git
 		then
 			module_clone "$path" "$url" "$reference"|| exit
+			cloned_modules="$cloned_modules;$name"
 			subsha1=
 		else
 			subsha1=$(clear_local_git_env; cd "$path" &&
@@ -469,6 +471,13 @@ cmd_update()
 				die "Unable to fetch in submodule path '$path'"
 			fi
 
+			# Is this something we just cloned?
+			case ";$cloned_modules;" in
+			*";$name;"*)
+				# then there is no local change to integrate
+				update_module= ;;
+			esac
+
 			case "$update_module" in
 			rebase)
 				command="git rebase"