Add fallback timeout documentation for when Gemstash's off/missing

[parndt]

Per rubygems/bundler#4186 this documents how to add a fallback timeout to prevent this happening when Gemstash is off:

$ bundle update
Fetching source index from http://localhost:9292/
Retrying fetcher due to error (2/4): Bundler::HTTPError Could not fetch specs from http://localhost:9292/
Retrying fetcher due to error (3/4): Bundler::HTTPError Could not fetch specs from http://localhost:9292/
Retrying fetcher due to error (4/4): Bundler::HTTPError Could not fetch specs from http://localhost:9292/
Could not fetch specs from http://localhost:9292/

After configuring a fallback, as described:

$ bundle config mirror.https://rubygems.org.fallback_timeout true

Instead, after trying Gemstash first and quickly failing, we see this:

$ bundle update
Fetching gem metadata from https://rubygems.org/
Fetching version metadata from https://rubygems.org/
Fetching dependency metadata from https://rubygems.org/

So we can see that it skips to using https://rubygems.org instead.

Now, Gemstash seems much more like a viable option for a mirror!

[pcarranza]

Glad you like it, I coded that feature myself 😄

We were missing documentation for this 👍

[parndt]

I suppose I should have set [ci skip]..

@pcarranza would you also like documentation for bundler.io?

[pcarranza]

@parndt Heh, I thought I did added documentation, but I did not.

Please do, it will be great to have it properly documented.

Don't worry about CI, this is just documentation and JRuby complaining is not something odd, sadly.

[pcarranza]

I'm merging with CI failing because it is not a code change, but a documentation change.

cc @smellsblue @indirect

[parndt]

@pcarranza @indirect @smellsblue I've also documented this for Bundler's documentation site over at rubygems/bundler-site#212

[indirect]

Thanks @parndt!

[smellsblue]

👍