submodule sync: skip work for inactive submodules

Sync does some work determining what URLs should be used for a submodule
but then throws this work away if the submodule isn't active.  Instead
perform the activity check earlier and skip inactive submodule in order
to avoid doing unnecessary work.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -1090,6 +1090,13 @@ cmd_sync()
 	do
 		die_if_unmatched "$mode" "$sha1"
 		name=$(git submodule--helper name "$sm_path")
+
+		# skip inactive submodules
+		if ! git config "submodule.$name.url" >/dev/null 2>/dev/null
+		then
+			continue
+		fi
+
 		url=$(git config -f .gitmodules --get submodule."$name".url)
 
 		# Possibly a url relative to parent
@@ -1111,27 +1118,24 @@ cmd_sync()
 			;;
 		esac
 
-		if git config "submodule.$name.url" >/dev/null 2>/dev/null
+		displaypath=$(git submodule--helper relative-path "$prefix$sm_path" "$wt_prefix")
+		say "$(eval_gettext "Synchronizing submodule url for '\$displaypath'")"
+		git config submodule."$name".url "$super_config_url"
+
+		if test -e "$sm_path"/.git
 		then
-			displaypath=$(git submodule--helper relative-path "$prefix$sm_path" "$wt_prefix")
+		(
-			say "$(eval_gettext "Synchronizing submodule url for '\$displaypath'")"
+			sanitize_submodule_env
-			git config submodule."$name".url "$super_config_url"
+			cd "$sm_path"
+			remote=$(get_default_remote)
+			git config remote."$remote".url "$sub_origin_url"
 
-			if test -e "$sm_path"/.git
+			if test -n "$recursive"
 			then
-			(
+				prefix="$prefix$sm_path/"
-				sanitize_submodule_env
+				eval cmd_sync
-				cd "$sm_path"
-				remote=$(get_default_remote)
-				git config remote."$remote".url "$sub_origin_url"
-
-				if test -n "$recursive"
-				then
-					prefix="$prefix$sm_path/"
-					eval cmd_sync
-				fi
-			)
 			fi
+		)
 		fi
 	done
 }