revlog: define ellipsis flag processors in core

We will soon be teaching core to honor the ellipsis flag on revlogs.
Moving the definition of the processor functions to core is the first
step in this.

The processor is still not registered unless the narrow extension is
loaded.

Differential Revision: https://phab.mercurial-scm.org/D4645

hgext/narrow/narrowrevlog.py

@@ -11,17 +11,7 b' from mercurial import ('
    revlog,
 )
 
-def readtransform(self, text):
-    return text, False
-
-def writetransform(self, text):
-    return text, False
-
-def rawtransform(self, text):
-    return False
-
-revlog.addflagprocessor(revlog.REVIDX_ELLIPSIS,
-                        (readtransform, writetransform, rawtransform))
+revlog.addflagprocessor(revlog.REVIDX_ELLIPSIS, revlog.ellipsisprocessor)
 
 def setup():
     # We just wanted to add the flag processor, which is done at module

mercurial/revlog.py

@@ -115,6 +115,22 b' ProgrammingError = error.ProgrammingErro'
     REVIDX_ISCENSORED: None,
 }
 
+# Flag processors for REVIDX_ELLIPSIS.
+def ellipsisreadprocessor(rl, text):
+    return text, False
+
+def ellipsiswriteprocessor(rl, text):
+    return text, False
+
+def ellipsisrawprocessor(rl, text):
+    return False
+
+ellipsisprocessor = (
+    ellipsisreadprocessor,
+    ellipsiswriteprocessor,
+    ellipsisrawprocessor,
+)
+
 _mdre = re.compile('\1\n')
 def parsemeta(text):
     """return (metadatadict, metadatasize)"""