flagprocessors: introduce specialized functions

flagprocessors: introduce specialized functions

This make the call site clearer and the open the way to more diverse return
types.

For now, the same old code is still in use under the hood.

Differential Revision: https://phab.mercurial-scm.org/D6800

--- a/mercurial/revlogutils/flagutil.py	Thu Aug 08 02:10:18 2019 +0200
+++ b/mercurial/revlogutils/flagutil.py	Fri Aug 30 18:54:36 2019 +0200
@@ -90,12 +90,20 @@
     _flagserrorclass = error.RevlogError
 
     def _processflags(self, text, flags, operation, raw=False):
-        """Inspect revision data flags and applies transforms defined by
-        registered flag processors.
+        """deprecated entry point to access flag processors"""
+        if raw:
+            return text, self._processflagsraw(text, flags)
+        elif operation == 'read':
+            return self._processflagsread(text, flags)
+        else: # write operation
+            return self._processflagswrite(text, flags)
+
+    def _processflagsread(self, text, flags):
+        """Inspect revision data flags and applies read transformations defined
+        by registered flag processors.
 
         ``text`` - the revision data to process
         ``flags`` - the revision flags
-        ``operation`` - the operation being performed (read or write)
         ``raw`` - an optional argument describing if the raw transform should be
         applied.
 
@@ -107,10 +115,46 @@
         Returns a 2-tuple of ``(text, validatehash)`` where ``text`` is the
         processed text and ``validatehash`` is a bool indicating whether the
         returned text should be checked for hash integrity.
+        """
+        return self._processflagsfunc(text, flags, 'read')
 
-        Note: If the ``raw`` argument is set, it has precedence over the
-        operation and will only update the value of ``validatehash``.
+    def _processflagswrite(self, text, flags):
+        """Inspect revision data flags and applies write transformations defined
+        by registered flag processors.
+
+        ``text`` - the revision data to process
+        ``flags`` - the revision flags
+
+        This method processes the flags in the order (or reverse order if
+        ``operation`` is 'write') defined by REVIDX_FLAGS_ORDER, applying the
+        flag processors registered for present flags. The order of flags defined
+        in REVIDX_FLAGS_ORDER needs to be stable to allow non-commutativity.
+
+        Returns a 2-tuple of ``(text, validatehash)`` where ``text`` is the
+        processed text and ``validatehash`` is a bool indicating whether the
+        returned text should be checked for hash integrity.
         """
+        return self._processflagsfunc(text, flags, 'write')
+
+    def _processflagsraw(self, text, flags):
+        """Inspect revision data flags to check is the content hash should be
+        validated.
+
+        ``text`` - the revision data to process
+        ``flags`` - the revision flags
+
+        This method processes the flags in the order (or reverse order if
+        ``operation`` is 'write') defined by REVIDX_FLAGS_ORDER, applying the
+        flag processors registered for present flags. The order of flags defined
+        in REVIDX_FLAGS_ORDER needs to be stable to allow non-commutativity.
+
+        Returns a 2-tuple of ``(text, validatehash)`` where ``text`` is the
+        processed text and ``validatehash`` is a bool indicating whether the
+        returned text should be checked for hash integrity.
+        """
+        return self._processflagsfunc(text, flags, 'read', raw=True)[1]
+
+    def _processflagsfunc(self, text, flags, operation, raw=False):
         # fast path: no flag processors will run
         if flags == 0:
             return text, True