txnTieKnot fix (~10% memory reduce) (#483)

* bin: ignore chart and dupes addons

* lib: fix txnTieKnot

Ensure that postings refers to their transaction rather than original
one.
This should allow compiler perform destructive update and/or allow
garbage collecting old transaction.

bin/.gitignore

@@ -1,4 +1,6 @@
+hledger-chart
 hledger-check-dates
+hledger-dupes
 hledger-equity
 hledger-print-unique
 hledger-register-match

hledger-lib/Hledger/Data/Transaction.hs

@@ -489,7 +489,8 @@ transactionDate2 t = fromMaybe (tdate t) $ tdate2 t
 -- | Ensure a transaction's postings refer back to it, so that eg
 -- relatedPostings works right.
 txnTieKnot :: Transaction -> Transaction
-txnTieKnot t@Transaction{tpostings=ps} = t{tpostings=map (postingSetTransaction t) ps}
+txnTieKnot t@Transaction{tpostings=ps} = t' where
+    t' = t{tpostings=map (postingSetTransaction t') ps}
 
 -- | Ensure a transaction's postings do not refer back to it, so that eg
 -- recursiveSize and GHCI's :sprint work right.