bundle2: fix raising errors during heads checking

If the heads on the server differ from the ones reported seen by the client at
bundle time, we raise a PushRaced exception. However, the part raising the
exception was broken.

To fix it, we move the PushRaced class in the error module so it can be
accessible everywhere without an import cycle.

A test is also added to prevent regression.

mercurial/bundle2.py

@@ -145,7 +145,7 b' import struct'
 import urllib
 import string
 
-import changegroup
+import changegroup, error
 from i18n import _
 
 _pack = struct.pack
@@ -730,7 +730,7 b' def handlechangegroup(op, inpart):'
         h = inpart.read(20)
     assert not h
     if heads != op.repo.heads():
-        raise exchange.PushRaced()
+        raise error.PushRaced()
 
 @parthandler('b2x:output')
 def handleoutput(op, inpart):

mercurial/error.py

@@ -94,3 +94,7 b' class SignalInterrupt(KeyboardInterrupt)'
 
 class SignatureError(Exception):
     pass
+
+class PushRaced(RuntimeError):
+    """An exception raised during unbundling that indicate a push race"""
+

mercurial/exchange.py

@@ -8,7 +8,7 b''
 from i18n import _
 from node import hex, nullid
 import errno, urllib
-import util, scmutil, changegroup, base85
+import util, scmutil, changegroup, base85, error
 import discovery, phases, obsolete, bookmarks, bundle2
 
 def readbundle(ui, fh, fname, vfs=None):
@@ -708,9 +708,6 b' def _getbundleextrapart(bundler, repo, s'
     """hook function to let extensions add parts to the requested bundle"""
     pass
 
-class PushRaced(RuntimeError):
-    """An exception raised during unbundling that indicate a push race"""
-
 def check_heads(repo, their_heads, context):
     """check if the heads of a repo have been modified
 
@@ -722,8 +719,8 b' def check_heads(repo, their_heads, conte'
             their_heads == ['hashed', heads_hash]):
         # someone else committed/pushed/unbundled while we
         # were transferring data
-        raise PushRaced('repository changed while %s - '
-                        'please try again' % context)
+        raise error.PushRaced('repository changed while %s - '
+                              'please try again' % context)
 
 def unbundle(repo, cg, heads, source, url):
     """Apply a bundle to a repo.

mercurial/localrepo.py

@@ -133,7 +133,7 b' class localpeer(peer.peerrepository):'
                 stream = util.chunkbuffer(ret.getchunks())
                 ret = bundle2.unbundle20(self.ui, stream)
             return ret
-        except exchange.PushRaced, exc:
+        except error.PushRaced, exc:
             raise error.ResponseError(_('push failed:'), exc.message)
 
     def lock(self):

mercurial/wireproto.py

@@ -826,5 +826,5 b' def unbundle(repo, proto, heads):'
         else:
             sys.stderr.write("abort: %s\n" % inst)
             return pushres(0)
-    except exchange.PushRaced, exc:
+    except error.PushRaced, exc:
         return pusherr(str(exc))

tests/test-bundle2.t

@@ -15,6 +15,7 b' Create an extension to test bundle2 API'
   > from mercurial import scmutil
   > from mercurial import discovery
   > from mercurial import changegroup
+  > from mercurial import error
   > cmdtable = {}
   > command = cmdutil.command(cmdtable)
   > 
@@ -59,6 +60,7 b' Create an extension to test bundle2 API'
   >           ('', 'unknown', False, 'include an unknown mandatory part in the bundle'),
   >           ('', 'parts', False, 'include some arbitrary parts to the bundle'),
   >           ('', 'reply', False, 'produce a reply bundle'),
+  >           ('', 'pushrace', False, 'includes a check:head part with unknown nodes'),
   >           ('r', 'rev', [], 'includes those changeset in the bundle'),],
   >          '[OUTPUTFILE]')
   > def cmdbundle2(ui, repo, path=None, **opts):
@@ -75,6 +77,10 b' Create an extension to test bundle2 API'
   >         capsstring = 'ping-pong\nelephants=babar,celeste\ncity%3D%21=celeste%2Cville'
   >         bundler.addpart(bundle2.bundlepart('b2x:replycaps', data=capsstring))
   > 
+  >     if opts['pushrace']:
+  >         dummynode = '01234567890123456789'
+  >         bundler.addpart(bundle2.bundlepart('b2x:check:heads', data=dummynode))
+  > 
   >     revs = opts['rev']
   >     if 'rev' in opts:
   >         revs = scmutil.revrange(repo, opts['rev'])
@@ -132,6 +138,8 b' Create an extension to test bundle2 API'
   >             tr.close()
   >         except KeyError, exc:
   >             raise util.Abort('missing support for %s' % exc)
+  >         except error.PushRaced, exc:
+  >             raise util.Abort('push race')
   >     finally:
   >         if tr is not None:
   >             tr.release()
@@ -601,6 +609,15 b' Unbundle the reply to get the output:'
   remote: replying to ping request (id 6)
   0 unread bytes
 
+Test push race detection
+
+  $ hg bundle2 --pushrace ../part-race.hg2
+
+  $ hg unbundle2 < ../part-race.hg2
+  0 unread bytes
+  abort: push race
+  [255]
+
 Support for changegroup
 ===================================