diff -r 94a4980695f8 -r 729082bb9938 mercurial/revlog.py
--- a/mercurial/revlog.py	Thu Jul 12 12:11:20 2018 -0700
+++ b/mercurial/revlog.py	Thu Aug 16 02:08:13 2018 +0200
@@ -36,6 +36,26 @@
     wdirrev,
 )
 from .i18n import _
+from .revlogutils.constants import (
+    FLAG_GENERALDELTA,
+    FLAG_INLINE_DATA,
+    LIMIT_DELTA2TEXT,
+    REVIDX_DEFAULT_FLAGS,
+    REVIDX_ELLIPSIS,
+    REVIDX_EXTSTORED,
+    REVIDX_FLAGS_ORDER,
+    REVIDX_ISCENSORED,
+    REVIDX_KNOWN_FLAGS,
+    REVIDX_RAWTEXT_CHANGING_FLAGS,
+    REVLOGV0,
+    REVLOGV1,
+    REVLOGV1_FLAGS,
+    REVLOGV2,
+    REVLOGV2_FLAGS,
+    REVLOG_DEFAULT_FLAGS,
+    REVLOG_DEFAULT_FORMAT,
+    REVLOG_DEFAULT_VERSION,
+)
 from .thirdparty import (
     attr,
 )
@@ -54,40 +74,31 @@
     stringutil,
 )
 
+# blanked usage of all the name to prevent pyflakes constraints
+# We need these name available in the module for extensions.
+REVLOGV0
+REVLOGV1
+REVLOGV2
+FLAG_INLINE_DATA
+FLAG_GENERALDELTA
+REVLOG_DEFAULT_FLAGS
+REVLOG_DEFAULT_FORMAT
+REVLOG_DEFAULT_VERSION
+REVLOGV1_FLAGS
+REVLOGV2_FLAGS
+REVIDX_ISCENSORED
+REVIDX_ELLIPSIS
+REVIDX_EXTSTORED
+REVIDX_DEFAULT_FLAGS
+REVIDX_FLAGS_ORDER
+REVIDX_KNOWN_FLAGS
+REVIDX_RAWTEXT_CHANGING_FLAGS
+
 parsers = policy.importmod(r'parsers')
 
 # Aliased for performance.
 _zlibdecompress = zlib.decompress
 
-# revlog header flags
-REVLOGV0 = 0
-REVLOGV1 = 1
-# Dummy value until file format is finalized.
-# Reminder: change the bounds check in revlog.__init__ when this is changed.
-REVLOGV2 = 0xDEAD
-FLAG_INLINE_DATA = (1 << 16)
-FLAG_GENERALDELTA = (1 << 17)
-REVLOG_DEFAULT_FLAGS = FLAG_INLINE_DATA
-REVLOG_DEFAULT_FORMAT = REVLOGV1
-REVLOG_DEFAULT_VERSION = REVLOG_DEFAULT_FORMAT | REVLOG_DEFAULT_FLAGS
-REVLOGV1_FLAGS = FLAG_INLINE_DATA | FLAG_GENERALDELTA
-REVLOGV2_FLAGS = REVLOGV1_FLAGS
-
-# revlog index flags
-REVIDX_ISCENSORED = (1 << 15) # revision has censor metadata, must be verified
-REVIDX_ELLIPSIS = (1 << 14) # revision hash does not match data (narrowhg)
-REVIDX_EXTSTORED = (1 << 13) # revision data is stored externally
-REVIDX_DEFAULT_FLAGS = 0
-# stable order in which flags need to be processed and their processors applied
-REVIDX_FLAGS_ORDER = [
-    REVIDX_ISCENSORED,
-    REVIDX_ELLIPSIS,
-    REVIDX_EXTSTORED,
-]
-REVIDX_KNOWN_FLAGS = util.bitsfrom(REVIDX_FLAGS_ORDER)
-# bitmark for flags that could cause rawdata content change
-REVIDX_RAWTEXT_CHANGING_FLAGS = REVIDX_ISCENSORED | REVIDX_EXTSTORED
-
 # max size of revlog with inline data
 _maxinline = 131072
 _chunksize = 1048576
@@ -854,9 +865,6 @@
             return (0, 0, 0, -1, -1, -1, -1, nullid)
         return list.__getitem__(self, i)
 
-# maximum <delta-chain-data>/<revision-text-length> ratio
-LIMIT_DELTA2TEXT = 2
-
 class revlogoldio(object):
     def __init__(self):
         self.size = indexformatv0.size