new file mode 100644
--- /dev/null
+++ b/hgsubversion/layouts/custom.py
@@ -0,0 +1,105 @@
+"""Layout that allows you to define arbitrary subversion to mercurial mappings.
+
+This is the simplest layout to use if your layout is just plain weird.
+Also useful if your layout is pretty normal, but you personally only
+want a couple of branches.
+
+
+"""
+
+import base
+
+
+class CustomLayout(base.BaseLayout):
+
+    def __init__(self, ui):
+        base.BaseLayout.__init__(self, ui)
+
+        self.svn_to_hg = {}
+        self.hg_to_svn = {}
+
+        for hg_branch, svn_path in ui.configitems('hgsubversionbranch'):
+
+            hg_branch = hg_branch.strip()
+            if hg_branch == 'default' or not hg_branch:
+                hg_branch = None
+            svn_path = svn_path.strip('/')
+
+            for other_svn in self.svn_to_hg:
+                if other_svn == svn_path:
+                    msg = 'specified two hg branches for svn path %s: %s and %s'
+                    raise hgutil.Abort(msg % (svn_path, other_hg, hg_branch))
+
+                if (other_svn.startswith(svn_path + '/') or
+                    svn_path.startswith(other_svn + '/')):
+                    msg = 'specified mappings for nested svn paths: %s and %s'
+                    raise hgutl.Abort(msg % (svn_path, other_svn))
+
+            self.svn_to_hg[svn_path] = hg_branch
+            self.hg_to_svn[hg_branch] = svn_path
+
+    def localname(self, path):
+        if path in self.svn_to_hg:
+            return self.svn_to_hg[path]
+        children = []
+        for svn_path in self.svn_to_hg:
+            if svn_path.startswith(path + '/'):
+                children.append(svn_path)
+        if len(children) == 1:
+            return self.svn_to_hg[children[0]]
+
+        return '../%s' % path
+
+    def remotename(self, branch):
+        if branch =='default':
+            branch = None
+        if branch and branch.startswith('../'):
+            return branch[3:]
+        if branch not in self.hg_to_svn:
+            raise KeyError('Unknown mercurial branch: %s' % branch)
+        return self.hg_to_svn[branch]
+
+    def remotepath(self, branch, subdir='/'):
+        if not subdir.endswith('/'):
+            subdir += '/'
+        return subdir + self.remotename(branch)
+
+    def taglocations(self, meta_data_dir):
+        return []
+
+    def get_path_tag(self, path, taglocations):
+        return None
+
+    def split_remote_name(self, path, known_branches):
+        if path in self.svn_to_hg:
+            return path, ''
+        children = []
+        for svn_path in self.svn_to_hg:
+            if path.startswith(svn_path + '/'):
+                return svn_path, path[len(svn_path)+1:]
+            if svn_path.startswith(path + '/'):
+                children.append(svn_path)
+
+        # if the path represents the parent of exactly one of our svn
+        # branches, treat it as though it were that branch, because
+        # that means we are probably pulling in a subproject of an svn
+        # project, and someone copied the parent svn project.
+        if len(children) == 1:
+            return children[0], ''
+
+        for branch in known_branches:
+            if branch and branch.startswith('../'):
+                if path.startswith(branch[3:] + '/'):
+                    # -3 for the leading ../, plus one for the trailing /
+                    return branch[3:], path[len(branch) - 2:]
+                if branch[3:].startswith(path + '/'):
+                    children.append(branch[3:])
+
+        if len(children) == 1:
+            return children[0], ''
+
+
+        # this splits on the rightmost '/' but considers the entire
+        # string to be the branch component of the path if there is no '/'
+        components = path.rsplit('/', 1)
+        return components[0], '/'.join(components[1:])