clone submodules shallow by default

which makes it vastly quicker and easier to get going with
these very large repos.

Change-Id: Ib1bb8e824a6a2228be13ab4379e7f5e660371cea
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/189002
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Jenkins

.gitmodules

@@ -2,11 +2,14 @@
 	path = dictionaries
 	url = ../dictionaries
 	branch = .
+    shallow = true
 [submodule "helpcontent2"]
 	path = helpcontent2
 	url = ../help
 	branch = .
+    shallow = true
 [submodule "translations"]
 	path = translations
 	url = ../translations
 	branch = .
+    shallow = true

g

@@ -296,9 +296,9 @@ do_init_modules()
     done
     for module in $SUBMODULES_CONFIGURED ; do
         if [ -n "$REFERENCED_GIT" ] ; then
-            git submodule update --reference "$REFERENCED_GIT/.git/modules/$module" --progress "$module" || return $?
+            git submodule update --depth 1 --reference "$REFERENCED_GIT/.git/modules/$module" --progress "$module" || return $?
         else
-            git submodule update --progress "$module" || return $?
+            git submodule update --depth 1 --progress "$module" || return $?
         fi
     done
     return 0