--- a/mercurial/revlogutils/flagutil.py	Thu Aug 08 01:04:48 2019 +0200
+++ b/mercurial/revlogutils/flagutil.py	Thu Aug 08 01:28:34 2019 +0200
@@ -14,10 +14,13 @@
     REVIDX_EXTSTORED,
     REVIDX_FLAGS_ORDER,
     REVIDX_ISCENSORED,
-    REVIDX_KNOWN_FLAGS,
     REVIDX_RAWTEXT_CHANGING_FLAGS,
 )
 
+from .. import (
+    util
+)
+
 # blanked usage of all the name to prevent pyflakes constraints
 # We need these name available in the module for extensions.
 REVIDX_ISCENSORED
@@ -25,9 +28,10 @@
 REVIDX_EXTSTORED
 REVIDX_DEFAULT_FLAGS
 REVIDX_FLAGS_ORDER
-REVIDX_KNOWN_FLAGS
 REVIDX_RAWTEXT_CHANGING_FLAGS
 
+REVIDX_KNOWN_FLAGS = util.bitsfrom(REVIDX_FLAGS_ORDER)
+
 # Store flag processors (cf. 'addflagprocessor()' to register)
 flagprocessors = {
     REVIDX_ISCENSORED: None,