Updated Mod Version Data Format (markdown)

Mod-Version-Data-Format.md

@@ -119,6 +119,17 @@ Please be sure to use these two commands prior to submitting a pull request for
 
   This command is required after each `recipe` command.
 
+* `onlyif: (not) <kind> <name>`
+
+  Makes the current recipe only available if some condition is met (or isn't met).  The possible `kind` attributes
+  are: `item` and `mod`.  In either case, the `name` attribute should then be the name of the item or mod which 
+  must be present (or not).
+
+  For example, the Basic Capacitor from EnderIO uses an Iron Ingot by default, but if there is some other mod
+  which adds a Copper Ingot, then it will use the copper instead.  In order to make the extra recipe only appear
+  when copper is available, use: `onlyif: item Copper Ingot`.  Then, in order to make the default recipe disappear
+  when copper is available, use: `onlyif: not item Copper Ingot`.
+
 * `pattern: <pattern>` _(required)_
 
   Describes the placement of each input item in the 3×3 crafting grid.  A pattern is an 11 character