revlog: get rid of defversion

defversion was a property (later option) on the store opener, used to propagate
the changelog revlog format to the other revlogs, so they would be created with
the same format.

This required that the changelog instance was created before any other revlog;
an invariant that wasn't directly enforced (or documented) anywhere.

We now use the revlogv1 requirement instead, which is transfered to the store
opener options. If this option is missing, v0 revlogs are created.

mercurial/localrepo.py

@@ -116,9 +116,9 b' class localrepository(repo.repository):'
 
     def _applyrequirements(self, requirements):
         self.requirements = requirements
-        self.sopener.options = {}
-        if 'generaldelta' in requirements:
-            self.sopener.options['generaldelta'] = 1
+        openerreqs = set(('revlogv1', 'generaldelta'))
+        self.sopener.options = dict((r, 1) for r in requirements
+                                           if r in openerreqs)
 
     def _writerequirements(self):
         reqfile = self.opener("requires", "w")
@@ -178,7 +178,6 b' class localrepository(repo.repository):'
             p = os.environ['HG_PENDING']
             if p.startswith(self.root):
                 c.readpending('00changelog.i.a')
-        self.sopener.options['defversion'] = c.version
         return c
 
     @propertycache

mercurial/revlog.py

@@ -227,12 +227,11 b' class revlog(object):'
 
         v = REVLOG_DEFAULT_VERSION
         if hasattr(opener, 'options'):
-            if 'defversion' in opener.options:
-                v = opener.options['defversion']
-                if v & REVLOGNG:
-                    v |= REVLOGNGINLINEDATA
-            if v & REVLOGNG and 'generaldelta' in opener.options:
-                v |= REVLOGGENERALDELTA
+            if 'revlogv1' in opener.options:
+                if 'generaldelta' in opener.options:
+                    v |= REVLOGGENERALDELTA
+            else:
+                v = 0
 
         i = ''
         try: