exchange: pass pushop to discovery.checkheads

Previously, we passed a bunch of parameters to discovery.checkheads, but all
of the arguments can be fetched out of pushop, which may contain a lot more
useful information for extensions now that pushop is extensible.

mercurial/discovery.py

@@ -255,12 +255,22 b' def _nowarnheads(repo, remote, newbookma'
 
     return bookmarkedheads
 
-def checkheads(repo, remote, outgoing, remoteheads, newbranch=False, inc=False,
-               newbookmarks=[]):
+def checkheads(pushop):
     """Check that a push won't add any outgoing head
 
     raise Abort error and display ui message as needed.
     """
+
+    repo = pushop.repo.unfiltered()
+    remote = pushop.remote
+    outgoing = pushop.outgoing
+    remoteheads = pushop.remoteheads
+    newbranch = pushop.newbranch
+    inc = bool(pushop.incoming)
+
+    # internal config: bookmarks.pushing
+    newbookmarks = pushop.ui.configlist('bookmarks', 'pushing')
+
     # Check for each named branch if we're creating new remote heads.
     # To be a remote head after push, node must be either:
     # - unknown locally

mercurial/exchange.py

@@ -571,13 +571,7 b' def _pushcheckoutgoing(pushop):'
                 elif ctx.troubled():
                     raise error.Abort(mst[ctx.troubles()[0]] % ctx)
 
-        # internal config: bookmarks.pushing
-        newbm = pushop.ui.configlist('bookmarks', 'pushing')
-        discovery.checkheads(unfi, pushop.remote, outgoing,
-                             pushop.remoteheads,
-                             pushop.newbranch,
-                             bool(pushop.incoming),
-                             newbm)
+        discovery.checkheads(pushop)
     return True
 
 # List of names of steps to perform for an outgoing bundle2, order matters.