[PATCH 3 of 3 V2] revlog: avoid applying delta chain on cache hit

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1491183613 25200
#      Sun Apr 02 18:40:13 2017 -0700
# Node ID 8324b03f08a91fd039ee83428b86792374640b89
# Parent  e5669675e4f24e98c99165c112fa81db66ff6094
# Available At https://bitbucket.org/quark-zju/hg-draft
#              hg pull https://bitbucket.org/quark-zju/hg-draft -r 8324b03f08a9
revlog: avoid applying delta chain on cache hit

Previously, revlog.revision(raw=False) may try to apply the delta chain
on _cache hit. That happens if flags are non-empty. This patch makes rawtext
reused so delta chain application is avoided.

"_cache" and "rev" are moved a bit to avoid unnecessary assignments.

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -1269,4 +1269,5 @@ class revlog(object):
         cachedrev = None
         flags = None
+        rawtext = None
         if node == nullid:
             return ""
@@ -1284,9 +1285,10 @@ class revlog(object):
                 if flags == REVIDX_DEFAULT_FLAGS:
                     return self._cache[2]
+                # rawtext is reusable. need to run flag processor
+                rawtext = self._cache[2]
 
             cachedrev = self._cache[1]
 
         # look up what we need to read
-        rawtext = None
         if rawtext is None:
             if rev is None:
@@ -1306,6 +1308,9 @@ class revlog(object):
 
             rawtext = mdiff.patches(rawtext, bins)
+            self._cache = (node, rev, rawtext)
 
         if flags is None:
+            if rev is None:
+                rev = self.rev(node)
             flags = self.flags(rev)
 
@@ -1314,5 +1319,4 @@ class revlog(object):
             self.checkhash(text, node, rev=rev)
 
-        self._cache = (node, rev, rawtext)
         return text