[PATCH 7 of 7 🚂] transaction: factorise append-only file registration

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at fb.com>
# Date 1415182381 0
#      Wed Nov 05 10:13:01 2014 +0000
# Node ID f7a9075b0999727f85493e9b61d9191f10111694
# Parent  7a4e0a8524b5efbf8eb0c6848bf316bfdfaa325b
transaction: factorise append-only file registration

The addition is done in two different places but differ slightly. We factorise
this addition to ensure it consistent in all place.

diff --git a/mercurial/transaction.py b/mercurial/transaction.py
--- a/mercurial/transaction.py
+++ b/mercurial/transaction.py
@@ -128,29 +128,28 @@ class transaction(object):
         """apply delayed registration of file entry.
 
         This is used by strip to delay vision of strip offset. The transaction
         see either none or all strip action to be done."""
         q = self._queue.pop()
-        self.entries.extend(q)
-
-        offsets = []
-        for f, o, _data in q:
-            offsets.append((f, o))
-
-        d = ''.join(['%s\0%d\n' % (f, o) for f, o in offsets])
-        self.file.write(d)
-        self.file.flush()
+        for f, o, data in q:
+            self._addentry(f, o, data)
 
     @active
     def add(self, file, offset, data=None):
         """record the state of an append-only file before update"""
         if file in self.map or file in self._backupmap:
             return
         if self._queue:
             self._queue[-1].append((file, offset, data))
             return
 
+        self._addentry(file, offset, data)
+
+    def _addentry(self, file, offset, data):
+        """add a append-only entry to memory and on-disk state"""
+        if file in self.map or file in self._backupmap:
+            return
         self.entries.append((file, offset, data))
         self.map[file] = len(self.entries) - 1
         # add enough data to the journal to do the truncate
         self.file.write("%s\0%d\n" % (file, offset))
         self.file.flush()