[PATCH 1 of 2] changelog: add a new method to get files modified by a changeset

[Laurent Charignon]

# HG changeset patch
# User Laurent Charignon <lcharignon at fb.com>
# Date 1450469125 28800
#      Fri Dec 18 12:05:25 2015 -0800
# Node ID 7f4515a7218a55d0cb6770dcc04f6bbccfdae8dc
# Parent  71aa5a26162d6e4a165b68f07b331e3e2eedc117
changelog: add a new method to get files modified by a changeset

This patch adds a new method "readfiles" to get the files modified by a
changeset. It extracts some logic from "read" to only return the files modified
by a changeset as efficiently as possible. This is used in the next patch to
speed up hg log <file|folder>

diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -360,6 +360,17 @@
         files = l[3:]
         return (manifest, user, (time, timezone), files, desc, extra)
 
+    def readfiles(self, node):
+        """
+        short version of read that only returns the files modified by the cset
+        """
+        text = self.revision(node)
+        if not text:
+            return (nullid, "", (0, 0), [], "", _defaultextra)
+        last = text.index("\n\n")
+        l = text[:last].split('\n')
+        return l[3:]
+
     def add(self, manifest, files, desc, transaction, p1, p2,
                   user, date=None, extra=None):
         # Convert to UTF-8 encoded bytestrings as the very first