manifestv2: set requires at repo creation time

While it should be safe to switch to the new manifest format on an
existing repo, let's keep it simple for now and make the configuration
have any effect only at repo creation time. If the configuration is
enabled then (at repo creation), we add an entry to requires and read
that instead of the configuration from then on.

tests/test-manifestv2.t

@@ -0,0 +1,31 b''
+Check that entry is added to .hg/requires
+
+  $ hg --config experimental.manifestv2=True init repo
+  $ cd repo
+  $ grep manifestv2 .hg/requires
+  manifestv2
+
+Set up simple repo
+
+  $ echo a > file1
+  $ echo b > file2
+  $ echo c > file3
+  $ hg ci -Aqm 'initial'
+  $ echo d > file2
+  $ hg ci -m 'modify file2'
+
+Check that 'hg verify', which uses manifest.readdelta(), works
+
+  $ hg verify
+  checking changesets
+  checking manifests
+  crosschecking files in changesets and manifests
+  checking files
+  3 files, 2 changesets, 4 total revisions
+
+TODO: Check that manifest revlog is smaller than for v1
+
+  $ hg debugindex -m
+     rev    offset  length   base linkrev nodeid       p1           p2
+       0         0     106      0       0 f6279f9f8b31 000000000000 000000000000
+       1       106      59      0       1 cd20459b75e6 f6279f9f8b31 000000000000

mercurial/localrepo.py

@@ -174,10 +174,10 b' class locallegacypeer(localpeer):'
 
 class localrepository(object):
 
-    supportedformats = set(('revlogv1', 'generaldelta'))
+    supportedformats = set(('revlogv1', 'generaldelta', 'manifestv2'))
     _basesupported = supportedformats | set(('store', 'fncache', 'shared',
                                              'dotencode'))
-    openerreqs = set(('revlogv1', 'generaldelta'))
+    openerreqs = set(('revlogv1', 'generaldelta', 'manifestv2'))
     requirements = ['revlogv1']
     filtername = None
 
@@ -241,6 +241,8 b' class localrepository(object):'
                     )
                 if self.ui.configbool('format', 'generaldelta', False):
                     requirements.append("generaldelta")
+                if self.ui.configbool('experimental', 'manifestv2', False):
+                    requirements.append("manifestv2")
                 requirements = set(requirements)
             else:
                 raise error.RepoError(_("repository %s not found") % path)
@@ -334,9 +336,6 b' class localrepository(object):'
         usetreemanifest = self.ui.configbool('experimental', 'treemanifest')
         if usetreemanifest is not None:
             self.svfs.options['usetreemanifest'] = usetreemanifest
-        usemanifestv2 = self.ui.configbool('experimental', 'manifestv2')
-        if usemanifestv2 is not None:
-            self.svfs.options['usemanifestv2'] = usemanifestv2
 
     def _writerequirements(self):
         reqfile = self.vfs("requires", "w")

mercurial/manifest.py

@@ -605,7 +605,7 b' class manifest(revlog.revlog):'
         if opts is not None:
             cachesize = opts.get('manifestcachesize', cachesize)
             usetreemanifest = opts.get('usetreemanifest', usetreemanifest)
-            usemanifestv2 = opts.get('usemanifestv2', usemanifestv2)
+            usemanifestv2 = opts.get('manifestv2', usemanifestv2)
         self._mancache = util.lrucachedict(cachesize)
         revlog.revlog.__init__(self, opener, "00manifest.i")
         self._usetreemanifest = usetreemanifest