revlog: deal with special "postfix" explicitely

revlog usually use a straight forward '.i' and '.d' naming except for two cases
"in-transaction" changelog, and censoring. Our goal is to let the revlog code
deal with the internal of the file naming itself. To do so, we need to start
dealing with these postfix explicitly.

Differential Revision: https://phab.mercurial-scm.org/D10571

mercurial/changelog.py

@@ -395,16 +395,19 b' class changelog(revlog.revlog):'
         ``concurrencychecker`` will be passed to the revlog init function, see
         the documentation there.
         """
+
+        indexfile = b'00changelog.i'
         if trypending and opener.exists(b'00changelog.i.a'):
-            indexfile = b'00changelog.i.a'
+            postfix = b'a'
         else:
-            indexfile = b'00changelog.i'
+            postfix = None
 
         datafile = b'00changelog.d'
         revlog.revlog.__init__(
             self,
             opener,
             target=(revlog_constants.KIND_CHANGELOG, None),
+            postfix=postfix,
             indexfile=indexfile,
             datafile=datafile,
             checkambig=True,

mercurial/revlog.py

@@ -289,6 +289,7 b' class revlog(object):'
         self,
         opener,
         target,
+        postfix=None,
         indexfile=None,
         datafile=None,
         checkambig=False,
@@ -312,9 +313,20 b' class revlog(object):'
         accurate value.
         """
         self.upperboundcomp = upperboundcomp
+        if not indexfile.endswith(b'.i'):
+            raise error.ProgrammingError(
+                b"revlog's indexfile should end with `.i`"
+            )
+        if datafile is None:
+            datafile = indexfile[:-2] + b".d"
+            if postfix is not None:
+                datafile = b'%s.%s' % (datafile, postfix)
+        if postfix is not None:
+            indexfile = b'%s.%s' % (indexfile, postfix)
         self.indexfile = indexfile
-        self.datafile = datafile or (indexfile[:-2] + b".d")
+        self.datafile = datafile
         self.nodemap_file = None
+        self.postfix = postfix
         if persistentnodemap:
             self.nodemap_file = nodemaputil.get_nodemap_file(
                 opener, self.indexfile
@@ -2881,16 +2893,13 b' class revlog(object):'
         # Rewriting the revlog in place is hard. Our strategy for censoring is
         # to create a new revlog, copy all revisions to it, then replace the
         # revlogs on transaction close.
-
-        newindexfile = self.indexfile + b'.tmpcensored'
-        newdatafile = self.datafile + b'.tmpcensored'
-
+        #
         # This is a bit dangerous. We could easily have a mismatch of state.
         newrl = revlog(
             self.opener,
             target=self.target,
-            indexfile=newindexfile,
-            datafile=newdatafile,
+            postfix=b'tmpcensored',
+            indexfile=self.indexfile,
             censorable=True,
         )
         newrl._format_version = self._format_version