new file mode 100644
--- /dev/null
+++ b/push_cmd.py
@@ -0,0 +1,114 @@
+from mercurial import util as merc_util
+from mercurial import hg
+from svn import core
+
+import util
+import hg_delta_editor
+import svnwrap
+import fetch_command
+import utility_commands
+
+
+@util.register_subcommand('push')
+@util.register_subcommand('dcommit') # for git expats
+def push_revisions_to_subversion(ui, repo, hg_repo_path, svn_url, **opts):
+    """Push revisions starting at a specified head back to Subversion.
+    """
+    #assert False # safety while the command is partially implemented.
+    hge = hg_delta_editor.HgChangeReceiver(hg_repo_path,
+                                           ui_=ui)
+    svn_commit_hashes = dict(zip(hge.revmap.itervalues(),
+                                 hge.revmap.iterkeys()))
+    # Strategy:
+    # 1. Find all outgoing commits from this head
+    outgoing = utility_commands.outgoing_revisions(ui, repo, hge,
+                                                   svn_commit_hashes)
+    if not (outgoing and len(outgoing)):
+        ui.status('No revisions to push.')
+        return 0
+    if len(repo.parents()) != 1:
+        ui.status('Cowardly refusing to push branch merge')
+        return 1
+    while outgoing:
+        oldest = outgoing.pop(-1)
+        old_ctx = repo[oldest]
+        if len(old_ctx.parents()) != 1:
+            ui.status('Found a branch merge, this needs discussion and '
+                      'implementation.')
+            return 1
+        base_n = old_ctx.parents()[0].node()
+        old_children = repo[base_n].children()
+        # 2. Commit oldest revision that needs to be pushed
+        base_revision = svn_commit_hashes[old_ctx.parents()[0].node()][0]
+        commit_from_rev(ui, repo, old_ctx, hge, svn_url, base_revision)
+        # 3. Fetch revisions from svn
+        r = fetch_command.fetch_revisions(ui, svn_url, hg_repo_path)
+        assert not r or r == 0
+        # 4. Find the new head of the target branch
+        repo = hg.repository(ui, hge.path)
+        base_c = repo[base_n]
+        replacement = [c for c in base_c.children() if c not in old_children
+                       and c.branch() == old_ctx.branch()]
+        assert len(replacement) == 1
+        replacement = replacement[0]
+        # 5. Rebase all children of the currently-pushing rev to the new branch
+        heads = repo.heads(old_ctx.node())
+        for needs_transplant in heads:
+            hg.clean(repo, needs_transplant)
+            utility_commands.rebase_commits(ui, repo, hg_repo_path, **opts)
+            repo = hg.repository(ui, hge.path)
+            if needs_transplant in outgoing:
+                hg.clean(repo, repo['tip'].node())
+                hge = hg_delta_editor.HgChangeReceiver(hg_repo_path, ui_=ui)
+                svn_commit_hashes = dict(zip(hge.revmap.itervalues(),
+                                             hge.revmap.iterkeys()))
+                outgoing = utility_commands.outgoing_revisions(ui, repo, hge,
+                                                              svn_commit_hashes)
+    return 0
+
+
+def commit_from_rev(ui, repo, rev_ctx, hg_editor, svn_url, base_revision):
+    """Build and send a commit from Mercurial to Subversion.
+    """
+    target_files = []
+    file_data = {}
+    for file in rev_ctx.files():
+        parent = rev_ctx.parents()[0]
+        new_data = base_data = ''
+        action = ''
+        if file in rev_ctx:
+            new_data = rev_ctx.filectx(file).data()
+            if file not in parent:
+                target_files.append(file)
+                action = 'add'
+                # TODO check for mime-type autoprops here
+                # TODO check for directory adds here
+            else:
+                target_files.append(file)
+                base_data = parent.filectx(file).data()
+                action = 'modify'
+        else:
+            target_files.append(file)
+            base_data = parent.filectx(file).data()
+            action = 'delete'
+        file_data[file] = base_data, new_data, action
+
+    # TODO check for directory deletes here
+    svn = svnwrap.SubversionRepo(svn_url)
+    parent_branch = rev_ctx.parents()[0].branch()
+    branch_path = 'trunk'
+    if parent_branch and parent_branch != 'default':
+        branch_path = 'branches/%s' % parent_branch
+    new_target_files = ['%s/%s' % (branch_path, f) for f in target_files]
+    for tf, ntf in zip(target_files, new_target_files):
+        if tf in file_data:
+            file_data[ntf] = file_data[tf]
+            del file_data[tf]
+    try:
+        svn.commit(new_target_files, rev_ctx.description(), file_data,
+                   base_revision, set([]))
+    except core.SubversionException, e:
+        if hasattr(e, 'apr_err') and e.apr_err == 160028:
+            raise merc_util.Abort('Base text was out of date, maybe rebase?')
+        else:
+            raise