diff -r 000000000000 -r 6474c204b198 tools/docs/mach_commands.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/docs/mach_commands.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,58 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, # You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import unicode_literals
+
+import os
+
+from mach.decorators import (
+    CommandArgument,
+    CommandProvider,
+    Command,
+)
+
+from mozbuild.base import MachCommandBase
+from mozbuild.frontend.reader import BuildReader
+
+
+@CommandProvider
+class Documentation(MachCommandBase):
+    """Helps manage in-tree documentation."""
+
+    @Command('build-docs', category='build-dev',
+        description='Generate documentation for the tree.')
+    @CommandArgument('--format', default='html',
+        help='Documentation format to write.')
+    @CommandArgument('outdir', default='<DEFAULT>', nargs='?',
+        help='Where to write output.')
+    def build_docs(self, format=None, outdir=None):
+        self._activate_virtualenv()
+        self.virtualenv_manager.install_pip_package('mdn-sphinx-theme==0.4')
+
+        from moztreedocs import SphinxManager
+
+        if outdir == '<DEFAULT>':
+            outdir = os.path.join(self.topobjdir, 'docs')
+
+        manager = SphinxManager(self.topsrcdir, os.path.join(self.topsrcdir,
+            'tools', 'docs'), outdir)
+
+        # We don't care about GYP projects, so don't process them. This makes
+        # scanning faster and may even prevent an exception.
+        def remove_gyp_dirs(sandbox):
+            sandbox['GYP_DIRS'][:] = []
+
+        reader = BuildReader(self.config_environment,
+            sandbox_post_eval_cb=remove_gyp_dirs)
+
+        for sandbox in reader.walk_topsrcdir():
+            for dest_dir, source_dir in sandbox['SPHINX_TREES'].items():
+                manager.add_tree(os.path.join(sandbox['RELATIVEDIR'],
+                    source_dir), dest_dir)
+
+            for entry in sandbox['SPHINX_PYTHON_PACKAGE_DIRS']:
+                manager.add_python_package_dir(os.path.join(sandbox['RELATIVEDIR'],
+                    entry))
+
+        return manager.generate_docs(format)