Make "yadm clone --recursive" work as expected.

The --recursive switch was ignored when YADM clones a dotfile repository.
This commit causes "yadm clone --recursive" to also clone submodules
in one go, similar to what GIT does when given the --recursive switch.

yadm

@@ -795,6 +795,7 @@ function clone() {
   DO_BOOTSTRAP=1
   local -a args
   local -i do_checkout=1
+  local -i do_submodules=0
   while [[ $# -gt 0 ]] ; do
     case "$1" in
       --bootstrap) # force bootstrap, without prompt
@@ -809,7 +810,10 @@ function clone() {
       -n|--no-checkout)
         do_checkout=0
       ;;
-      --bare|--mirror|--recurse-submodules*|--recursive|--separate-git-dir=*)
+      --recursive)
+        do_submodules=1
+      ;;
+      --bare|--mirror|--recurse-submodules*|--separate-git-dir=*)
         # ignore arguments without separate parameter
       ;;
       --separate-git-dir)
@@ -876,6 +880,10 @@ function clone() {
           "$GIT_PROGRAM" checkout -- ":/$file"
       done
 
+      if [[ $do_submodules -ne 0 ]]; then
+          "$GIT_PROGRAM" submodule update --init --recursive
+      fi
+
       if [ -n "$("$GIT_PROGRAM" ls-files --modified)" ]; then
         local msg
         IFS='' read -r -d '' msg <<EOF