Remove separate script for nightly devsite diff (#4105)

After the v0.11 release there is no need for a separate script for the extra modules.
I also added the fix for the code_prefix_url which should fix the issue with the broken "View Source" functionality.
An unrelated nit that I changed is the default value for the site_url parameter - we had this URL structure when we first had the internal staging site hosted on tensorflow's site, now it's in line with what we have live. 

For the next module extractions this script will need to cater for both the stable (v0.11) and the nightly (from master) version, it will be more manageable that way.

Fixes #4066.
Fixes #4104.

dev_tools/docs/build_api_docs.py

@@ -14,10 +14,15 @@
 # ==============================================================================
 """Tool to generate external api_docs for Cirq.
 
-This version is for the stable docs building that uses the v0.10 monolithic cirq
-module. This will be replaced with build_api_docs_multi_module.py after v0.11 is
-released.
+In order to publish to our site, devsite runs two jobs for us: stable and nightly.
+The stable one downloads the latest cirq release from pypi and uses that to generate the reference
+API docs.
+The nightly one downloads the latest cirq pre-release (pip install cirq --pre) and uses that to
+generate the "nightly diff".
+
+This script needs to cater for both of these cases.
 """
+
 import os
 import types
 
@@ -29,19 +34,21 @@
 from tensorflow_docs.api_generator import public_api
 
 import cirq
+import cirq_google
+
 from cirq import _doc
 
-flags.DEFINE_string("output_dir", "/tmp/cirq_api", "Where to output the docs")
+flags.DEFINE_string("output_dir", "docs/api_docs", "Where to output the docs")
 
 flags.DEFINE_string(
     "code_url_prefix",
-    "https://github.com/quantumlib/cirq/tree/master/cirq",
+    "https://github.com/quantumlib/Cirq/blob/master",
     "The url prefix for links to code.",
 )
 
 flags.DEFINE_bool("search_hints", True, "Include metadata search hints in the generated files")
 
-flags.DEFINE_string("site_path", "quark/cirq/api_docs/python", "Path prefix in the _toc.yaml")
+flags.DEFINE_string("site_path", "reference/python", "Path prefix in the _toc.yaml")
 
 FLAGS = flags.FLAGS
 
@@ -64,20 +71,19 @@ def filter_unwanted_inherited_methods(path, parent, children):
 
 
 def main(unused_argv):
+    generate_cirq()
+    generate_cirq_google()
+
+
+def generate_cirq():
     doc_generator = generate_lib.DocGenerator(
         root_title="Cirq",
         py_modules=[("cirq", cirq)],
         base_dir=os.path.dirname(cirq.__file__),
-        code_url_prefix=FLAGS.code_url_prefix,
+        code_url_prefix=FLAGS.code_url_prefix + "/cirq-core/cirq",
         search_hints=FLAGS.search_hints,
         site_path=FLAGS.site_path,
         callbacks=[public_api.local_definitions_filter, filter_unwanted_inherited_methods],
-        private_map={
-            # Opt to not build docs for these paths for now since they error.
-            "cirq.google.engine.client.quantum.QuantumEngineServiceClient": ["enums"],
-            "cirq.google.engine.client.quantum_v1alpha1.QuantumEngineServiceClient": ["enums"],
-            "cirq.google.api": ["v1"],
-        },
         extra_docs=_doc.RECORDED_CONST_DOCS,
     )
     doc_controls.decorate_all_class_attributes(
@@ -86,5 +92,25 @@ def main(unused_argv):
     doc_generator.build(output_dir=FLAGS.output_dir)
 
 
+def generate_cirq_google():
+    doc_generator = generate_lib.DocGenerator(
+        root_title="Cirq-google",
+        py_modules=[("cirq_google", cirq_google)],
+        base_dir=os.path.dirname(cirq_google.__file__),
+        code_url_prefix=FLAGS.code_url_prefix + "/cirq-google/cirq_google",
+        search_hints=FLAGS.search_hints,
+        site_path=FLAGS.site_path,
+        callbacks=[public_api.local_definitions_filter, filter_unwanted_inherited_methods],
+        private_map={
+            # Opt to not build docs for these paths for now since they error.
+            "cirq_google.engine.client.quantum.QuantumEngineServiceClient": ["enums"],
+            "cirq_google.engine.client.quantum_v1alpha1.QuantumEngineServiceClient": ["enums"],
+            "cirq_google.api": ["v1"],
+        },
+        extra_docs=_doc.RECORDED_CONST_DOCS,
+    )
+    doc_generator.build(output_dir=FLAGS.output_dir)
+
+
 if __name__ == "__main__":
     app.run(main)