remote-hg: force remote push

Ideally we shouldn't do this, as it's not recommended in mercurial
documentation, but there's no other way to push multiple bookmarks (on
the same branch), which would be the behavior most similar to git.

At the same time, add a configuration option for the people that don't
want to risk creating new remote heads.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/remote-helpers/git-remote-hg

@@ -27,6 +27,9 @@ import urllib
 # named branches:
 # git config --global remote-hg.track-branches false
 #
+# If you don't want to force pushes (and thus risk creating new remote heads):
+# git config --global remote-hg.force-push false
+#
 # git:
 # Sensible defaults for git.
 # hg bookmarks are exported as git branches, hg branches are prefixed
@@ -730,7 +733,7 @@ def do_export(parser):
             continue
 
     if peer:
-        parser.repo.push(peer, force=False)
+        parser.repo.push(peer, force=force_push)
 
     # handle bookmarks
     for bmark, node in p_bmarks:
@@ -773,20 +776,24 @@ def main(args):
     global prefix, dirname, branches, bmarks
     global marks, blob_marks, parsed_refs
     global peer, mode, bad_mail, bad_name
-    global track_branches
+    global track_branches, force_push
 
     alias = args[1]
     url = args[2]
     peer = None
 
     hg_git_compat = False
     track_branches = True
+    force_push = True
+
     try:
         if get_config('remote-hg.hg-git-compat') == 'true\n':
             hg_git_compat = True
             track_branches = False
         if get_config('remote-hg.track-branches') == 'false\n':
             track_branches = False
+        if get_config('remote-hg.force-push') == 'false\n':
+            force_push = False
     except subprocess.CalledProcessError:
         pass