[PATCH 3 of 7] transaction: add onclose hook for pre-close logic

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1395701867 25200
#      Mon Mar 24 15:57:47 2014 -0700
# Node ID c84f51f8f92e0a3db4888ac9739f43fd866cac20
# Parent  08595987c5b0e8af5aa8fec4debd7260f5a79e8f
transaction: add onclose hook for pre-close logic

Adds an optional onclose parameter to transactions that gets called just before
the transaction is committed. This allows things that build up data over the
course of the transaction (like the fncache) to commit their data.

diff --git a/mercurial/transaction.py b/mercurial/transaction.py
--- a/mercurial/transaction.py
+++ b/mercurial/transaction.py
@@ -42,12 +42,14 @@
     opener.unlink(journal)
 
 class transaction(object):
-    def __init__(self, report, opener, journal, after=None, createmode=None):
+    def __init__(self, report, opener, journal, after=None, createmode=None,
+            onclose=None):
         self.count = 1
         self.usages = 1
         self.report = report
         self.opener = opener
         self.after = after
+        self.onclose = onclose
         self.entries = []
         self.map = {}
         self.journal = journal
@@ -126,6 +128,9 @@
     @active
     def close(self):
         '''commit the transaction'''
+        if self.count == 1 and self.onclose:
+            self.onclose()
+
         self.count -= 1
         if self.count != 0:
             return