Add --shallow option

Provides the capability to make shallow clones (including submodules) to deploy
repositories with huge history.

Note that this might not work with some servers (github.com) if the commit
that is required by a submodule is too far away from any reference.

cdist/conf/type/__git/gencode-remote

@@ -36,6 +36,7 @@ group=$(cat "$__object/parameter/group")
 mode=$(cat "$__object/parameter/mode")
 
 [ -f "$__object/parameter/recursive" ] && recursive='--recurse-submodules' || recursive=''
+[ -f "$__object/parameter/shallow" ] && shallow='--depth 1 --shallow-submodules' || shallow=''
 
 [ "$state_should" = "$state_is" ] \
  && [ "$owner" = "$owner_is" ] \
@@ -45,7 +46,7 @@ mode=$(cat "$__object/parameter/mode")
 case $state_should in
     present)
         if [ "$state_should" != "$state_is" ]; then
-            echo git clone --quiet "$recursive" --branch "$branch" "$source" "$destination"
+            echo git clone --quiet "$recursive" "$shallow" --branch "$branch" "$source" "$destination"
         fi
         if { [ -n "$owner" ] && [ "$owner_is" != "$owner" ]; } || \
            { [ -n "$group" ] && [ "$group_is" != "$group" ]; }; then

cdist/conf/type/__git/man.rst

@@ -38,6 +38,10 @@ owner
 recursive
    Passes the --recurse-submodules flag to git when cloning the repository.
 
+shallow
+   Sets --depth=1 and --shallow-submodules for cloning repositories with big history.
+
+
 EXAMPLES
 --------
 

cdist/conf/type/__git/parameter/boolean

@@ -1 +1,2 @@
 recursive
+shallow