Appending working for library_list.json

pkg/docgen/README.md

 docgen
 ======
 
 A documentation generator for Dart.
 - - -
 The docgen tool takes in a file or directory as input and produces documentation
 for all `.dart` file it finds as YAML or JSON files. This outputs information 
 about all classes, variables, functions, and methods defined in the library and 
 its imported libraries.
 
@@ skipping 14 matching lines @@
 YAML files can be generated using the docgen package in the dart repository. 
 
 ###### Usage 
 
 Run  `dart docgen.dart [OPTIONS] <path to directory or file>`
 
 ###### Options available
 
 - `-h`, `--help` Prints help and usage information.
 - `-v`, `--verbose` Output more logging information.
-- `-j`, `--[no-]json` Outputs to JSON. Files are outputted to YAML by default.
+- `-j`, `--[no-]json` Outputs to JSON. Files are outputted to YAML by default. 
+If `--append` is used, it takes the file-format of the previous run stated in 
+library_list.json ignoring the flag.
 - `--include-private` Flag to include private declarations.
 - `--include-sdk` Flag to parse SDK Library files imported.
 - `--parse-sdk` Parses the SDK libraries only. (Ignores the path passed in.)
 - `--package-root` Sets the package root of the library being analyzed.
-- `--append` Appends to the docs folder, library_list.txt, and index.txt.
+- `--append` Appends to the docs folder, library_list.json, and index.txt.
 - `--introduction` Adds the provided markdown text file as the introduction
 for the outputted documentation.
 
 
 ###### Output Directory
 Documented libraries will be located at bin/docs in either YAML or JSON format 
-depending on options specified. There will also be a library_list.txt, 
+depending on options specified. There will also be a library_list.json, 
 containing a list of all the libraries inside the docs folder. 
 
 To get more information on how to use the outputted documentation with 
 dartdoc-viewer, please take a look at the 
 [dartdoc-viewer documentation][dartdoc-viewer].
 
 #### Uploading to Cloud Storage
 
 To push new files to Google Cloud Storage for use by the viewer, use the 
 `gsutil` tool located at third_party/gsutil/gsutil in the Dart repository.
@@ skipping 50 matching lines @@
  (ex. `--options='--include-sdk files'`).
  2. The `--gae-sdk` option gives the absolute path to the 
  [Google App Engine SDK][GAE]. 
 
 Running `python dartdoc.py --options=<docgen options> --gae-sdk=<path to SDK>` 
 will serve files generated by `docgen.dart` in your browser.
 
 [dartdoc-viewer]: https://github.com/dart-lang/dartdoc-viewer "Dartdoc-Viewer"
 [GAE]: https://developers.google.com/appengine/downloads#Google_App_Engine_SDK_for_Python  "Google App Engine SDK for Python"