Move "libraries.md" out of docs, onto the main site. (apache#3159)

docs/_bin/make-redirects.py

@@ -30,15 +30,16 @@ def normalize_target(redirect):
   source = redirect["source"]
   target = redirect["target"]
   source_file = os.path.join(docs_directory, source)
-  target_file = os.path.join(docs_directory, normalize_target(redirect))
 
   # Ensure redirect source doesn't exist yet.
   if os.path.exists(source_file):
     raise Exception('Redirect source is an actual file: ' + source)
 
-  # Ensure target *does* exist.
-  if not os.path.exists(target_file) and source not in all_sources:
-    raise Exception('Redirect target does not exist for source: ' + source)
+  # Ensure target *does* exist, if relative.
+  if not target.startswith("/"):
+    target_file = os.path.join(docs_directory, normalize_target(redirect))
+    if not os.path.exists(target_file) and source not in all_sources:
+      raise Exception('Redirect target does not exist for source: ' + source)
 
   # Write redirect file
   with open(source_file, 'w') as f:

docs/_redirects.json

@@ -44,7 +44,7 @@
   {"source": "Ingestion-overview.html", "target": "tutorials/ingestion.html"},
   {"source": "Ingestion.html", "target": "ingestion/index.html"},
   {"source": "Integrating-Druid-With-Other-Technologies.html", "target": "development/integrating-druid-with-other-technologies.html"},
-  {"source": "Libraries.html", "target": "development/libraries.html"},
+  {"source": "Libraries.html", "target": "/libraries.html"},
   {"source": "LimitSpec.html", "target": "querying/limitspec.html"},
   {"source": "Logging.html", "target": "configuration/logging.html"},
   {"source": "Metadata-storage.html", "target": "dependencies/metadata-storage.html"},
@@ -95,6 +95,7 @@
   {"source": "design/concepts-and-terminology.html", "target": "index.html"},
   {"source": "development/approximate-histograms.html", "target": "extensions-core/approximate-histograms.html"},
   {"source": "development/datasketches-aggregators.html", "target": "extensions-core/datasketches-aggregators.html"},
+  {"source": "development/libraries.html", "target": "/libraries.html"},
   {"source": "development/kafka-simple-consumer-firehose.html", "target": "extensions-contrib/kafka-simple.html"},
   {"source": "development/select-query.html", "target": "../querying/select-query.html"},
   {"source": "index.html", "target": "design/index.html"},