discovery: factor out calculation of heads to not warn about

In addition to taking a step towards getting an unreasonably large function
factored into smaller, more manageable functions, this will allow extensions
such as remotenames have more control over what pushes are allowed or not.

mercurial/discovery.py

@@ -238,6 +238,23 b' def _oldheadssummary(repo, remoteheads, '
         unsynced = set()
     return {None: (oldheads, newheads, unsynced)}
 
+def _nowarnheads(repo, remote, newbookmarks):
+    # Compute newly pushed bookmarks. We don't warn about bookmarked heads.
+    localbookmarks = repo._bookmarks
+    remotebookmarks = remote.listkeys('bookmarks')
+    bookmarkedheads = set()
+    for bm in localbookmarks:
+        rnode = remotebookmarks.get(bm)
+        if rnode and rnode in repo:
+            lctx, rctx = repo[bm], repo[rnode]
+            if bookmarks.validdest(repo, rctx, lctx):
+                bookmarkedheads.add(lctx.node())
+        else:
+            if bm in newbookmarks and bm not in remotebookmarks:
+                bookmarkedheads.add(repo[bm].node())
+
+    return bookmarkedheads
+
 def checkheads(repo, remote, outgoing, remoteheads, newbranch=False, inc=False,
                newbookmarks=[]):
     """Check that a push won't add any outgoing head
@@ -268,19 +285,8 b' def checkheads(repo, remote, outgoing, r'
                          hint=_("use 'hg push --new-branch' to create"
                                 " new remote branches"))
 
-    # 2. Compute newly pushed bookmarks. We don't warn about bookmarked heads.
-    localbookmarks = repo._bookmarks
-    remotebookmarks = remote.listkeys('bookmarks')
-    bookmarkedheads = set()
-    for bm in localbookmarks:
-        rnode = remotebookmarks.get(bm)
-        if rnode and rnode in repo:
-            lctx, rctx = repo[bm], repo[rnode]
-            if bookmarks.validdest(repo, rctx, lctx):
-                bookmarkedheads.add(lctx.node())
-        else:
-            if bm in newbookmarks and bm not in remotebookmarks:
-                bookmarkedheads.add(repo[bm].node())
+    # 2. Find heads that we need not warn about
+    nowarnheads = _nowarnheads(repo, remote, newbookmarks)
 
     # 3. Check for new heads.
     # If there are more heads after the push than before, a suitable
@@ -366,7 +372,7 b' def checkheads(repo, remote, outgoing, r'
                              " pushing new heads")
         elif len(newhs) > len(oldhs):
             # remove bookmarked or existing remote heads from the new heads list
-            dhs = sorted(newhs - bookmarkedheads - oldhs)
+            dhs = sorted(newhs - nowarnheads - oldhs)
         if dhs:
             if errormsg is None:
                 if branch not in ('default', None):