Update README

README.md

@@ -429,6 +429,7 @@ A typical mapping file might look like:
     /MACY'S/,"Macy's, Inc.",Expenses:Food
     MY COMPANY 1234,My Company,Income:Salary
     MY COMPANY 1234,My Company 1234,Income:Salary:Tips
+    MY TRANSFER 1,Transfer to Savings,Transfers:Savings,transfer_to=Assets:Savings
 
 It uses simple string-matching by default, but if you put a '/' at the
 start and end of a string it will instead be interpreted as a regular
@@ -438,6 +439,24 @@ Mapping is based on your historical decisions. Later matching entries
 overwrite earlier ones, that is in example above `MY COMPANY 1234` will
 be mapped to `My Company 1234` and `Income:Salary:Tips`.
 
+**Experimental**
+You can use `transfer_to=` to another asset to make the transfer to record in a "transfer"
+double-entry pattern.
+In the example above for the Transfers:Savings account with the transfer_to=Assets:Savings
+would create the following entries:
+
+2012/01/01 Transfer to Savings
+ Transfers:Savings  $100
+ Assets:Checking
+
+2012/01/01 Transfer to Savings
+ Assets:Savings  $100
+ Transfers:Savings
+
+You can additionally add a `file=` value after `transfer_to=` to write the second entry in another file.
+This is useful if you split your accounts per file and want to write the first transaction in the checking file
+and the second in the savings file.
+
 Accounts File
 --------------