The biggest problem when developing offline is the unavailability of documentation.
Google AppEngine used to provide a downloadable tar ball of its documentation, but doesn't seem to do so any more. So how do I get a local version of the AppEngine documentation, along with the ability to update it when required?
The solution to my problem turned out to be to use wget to create a local mirror of GAE/J's documentation.
pushd ~/Docs
wget --mirror -nH -np --page-requisites --convert-links --cut-dirs=3 \
-P GAEJ \
https://developers.google.com/appengine/docs/java/
Since the Q&A format of StackOverflow favours to-the-point answers, I wrote up a blog post with some more details (and for a more general use case): Downloading or Caching (Technical) Documentation.
Source: https://groups.google.com/forum/#!topic/google-appengine/mj_VA3UCkD8
Actual command:
httrack -N100 -%k https://developers.google.com/appengine/docs/java/
