Document defaults for buffer.copy()

doc/api/buffers.markdown

@@ -113,7 +113,7 @@ buffer object.  It does not change when the contents of the buffer are changed.
     // 1234
     // 1234
 
-### buffer.copy(targetBuffer, targetStart, sourceStart, sourceEnd=buffer.length)
+### buffer.copy(targetBuffer, targetStart, sourceStart=0, sourceEnd=buffer.length)
 
 Does a memcpy() between buffers.
 

lib/buffer.js

@@ -280,7 +280,7 @@ Buffer.prototype.toString = function (encoding, start, end) {
 Buffer.byteLength = SlowBuffer.byteLength;
 
 
-// copy(targetBuffer, targetStart, sourceStart, sourceEnd=buffer.length)
+// copy(targetBuffer, targetStart, sourceStart=0, sourceEnd=buffer.length)
 Buffer.prototype.copy = function copy (target, target_start, start, end) {
   var source = this;
   start || (start = 0);