localrepo: make supported features manageable in each repositories individually

Before this patch, all localrepositories support same features,
because supported features are managed by the class variable
"supported" of "localrepository".

For example, "largefiles" feature provided by largefiles extension is
recognized as supported, by adding the feature name to "supported" of
"localrepository".

So, commands handling multiple repositories at a time like below
misunderstand that such features are supported also in repositories
not enabling corresponded extensions:

  - clone/pull from or push to localhost
  - recursive execution in subrepo tree

"reposetup()" can't be used to fix this problem, because it is invoked
after checking whether supported features satisfy ones required in the
target repository.

So, this patch adds the set object named as "featuresetupfuncs" to
"localrepository" to manage hook functions to setup supported features
of each repositories.

If any functions are added to "featuresetupfuncs", they are invoked,
and information about supported features is managed in each
repositories individually.

This patch also adds checking below:

  - pull from localhost: whether features supported in the local(= dst)
    repository satisfies ones required in the remote(= src)

  - push to localhost: whether features supported in the remote(= dst)
    repository satisfies ones required in the local(= src)

Managing supported features by the class variable means that there is
no difference of supported features between each instances of
"localrepository" in the same Python process, so such checking is not
needed before this patch.

Even with this patch, if intermediate bundlefile is used as pulling
source, pulling indirectly from the remote repository, which requires
features more than ones supported in the local, can't be prevented,
because bundlefile has no information about "required features" in it.

hgext/largefiles/uisetup.py

@@ -153,7 +153,7 b' def uisetup(ui):'
     httppeer.httppeer._callstream = proto.httprepocallstream
 
     # don't die on seeing a repo with the largefiles requirement
-    localrepo.localrepository.supported |= set(['largefiles'])
+    localrepo.localrepository._basesupported |= set(['largefiles'])
 
     # override some extensions' stuff as well
     for name, module in extensions.extensions():

mercurial/localrepo.py

@@ -146,12 +146,14 b' class locallegacypeer(localpeer):'
 class localrepository(object):
 
     supportedformats = set(('revlogv1', 'generaldelta'))
-    supported = supportedformats | set(('store', 'fncache', 'shared',
+    _basesupported = supportedformats | set(('store', 'fncache', 'shared',
                                         'dotencode'))
     openerreqs = set(('revlogv1', 'generaldelta'))
     requirements = ['revlogv1']
     filtername = None
 
+    featuresetupfuncs = set()
+
     def _baserequirements(self, create):
         return self.requirements[:]
 
@@ -176,6 +178,13 b' class localrepository(object):'
         except IOError:
             pass
 
+        if self.featuresetupfuncs:
+            self.supported = set(self._basesupported) # use private copy
+            for setupfunc in self.featuresetupfuncs:
+                setupfunc(self.ui, self.supported)
+        else:
+            self.supported = self._basesupported
+
         if not self.vfs.isdir():
             if create:
                 if not self.wvfs.exists():
@@ -1649,6 +1658,14 b' class localrepository(object):'
         return r
 
     def pull(self, remote, heads=None, force=False):
+        if remote.local():
+            missing = set(remote.requirements) - self.supported
+            if missing:
+                msg = _("required features are not"
+                        " supported in the destination:"
+                        " %s") % (', '.join(sorted(missing)))
+                raise util.Abort(msg)
+
         # don't open transaction for nothing or you break future useful
         # rollback call
         tr = None
@@ -1749,6 +1766,14 b' class localrepository(object):'
             we have outgoing changesets but refused to push
           - other values as described by addchangegroup()
         '''
+        if remote.local():
+            missing = set(self.requirements) - remote.local().supported
+            if missing:
+                msg = _("required features are not"
+                        " supported in the destination:"
+                        " %s") % (', '.join(sorted(missing)))
+                raise util.Abort(msg)
+
         # there are two ways to push to remote repo:
         #
         # addchangegroup assumes local user can lock remote

mercurial/statichttprepo.py

@@ -89,6 +89,8 b' class statichttppeer(localrepo.localpeer'
         return False
 
 class statichttprepository(localrepo.localrepository):
+    supported = localrepo.localrepository._basesupported
+
     def __init__(self, ui, path):
         self._url = path
         self.ui = ui

tests/test-requires.t

@@ -15,5 +15,55 b''
   $ hg tip
   abort: unknown repository format: requires features 'indoor-pool', 'outdoor-pool' (upgrade Mercurial)!
   [255]
+  $ cd ..
+
+Test checking between features supported locally and ones required in
+another repository of push/pull/clone on localhost:
+
+  $ mkdir supported-locally
+  $ cd supported-locally
+
+  $ hg init supported
+  $ echo a > supported/a
+  $ hg -R supported commit -Am '#0 at supported'
+  adding a
+
+  $ echo 'featuresetup-test' >> supported/.hg/requires
+  $ cat > $TESTTMP/supported-locally/supportlocally.py <<EOF
+  > from mercurial import localrepo, extensions
+  > def featuresetup(ui, supported):
+  >     for name, module in extensions.extensions(ui):
+  >         if __name__ == module.__name__:
+  >             # support specific feature locally
+  >             supported |= set(['featuresetup-test'])
+  >             return
+  > def uisetup(ui):
+  >     localrepo.localrepository.featuresetupfuncs.add(featuresetup)
+  > EOF
+  $ cat > supported/.hg/hgrc <<EOF
+  > [extensions]
+  > # enable extension locally
+  > supportlocally = $TESTTMP/supported-locally/supportlocally.py
+  > EOF
+  $ hg -R supported status
+
+  $ hg init push-dst
+  $ hg -R supported push push-dst
+  pushing to push-dst
+  abort: required features are not supported in the destination: featuresetup-test
+  [255]
+
+  $ hg init pull-src
+  $ hg -R pull-src pull supported
+  pulling from supported
+  abort: required features are not supported in the destination: featuresetup-test
+  [255]
+
+  $ hg clone supported clone-dst
+  abort: unknown repository format: requires features 'featuresetup-test' (upgrade Mercurial)!
+  [255]
+  $ hg clone --pull supported clone-dst
+  abort: required features are not supported in the destination: featuresetup-test
+  [255]
 
   $ cd ..