Refresh Facebook CDN URLs on deploy

[dentarg]

Idea to address #1:

• Make _plugins/remote_facebook_photos.rb read app_secret from ENV (as a fallback, if possible? to not need ENV locally (e.g. Windows))
• Add the facebook app secret to env.secure in .travis.yml
• Remove the files in_data/facebook
• Exclude any files in _data/facebookfrom git

Then every deploy would refresh the Facebook CDN URLs.

Pros:

• no need to save even more images in the git repo

Cons:

• deploy would take longer, currently takes ~50s (see build history), locally doing jekyll build with empty _data/facebook directory reported done in 74.092 seconds. today
• working iteratively, pushing many commits would build up a big deploy backlog and the Facebook API might not like it?
• ENV is tricky business on Windows might be able to continue to use jekyll configuration locally

[dentarg]

Using Travis CI Cron Jobs, some of the cons above would be addressed, it's possible to make a difference on regular deploy and cron:

To check whether a build was triggered by cron, examine the TRAVIS_EVENT_TYPE environment variable to see if it has the value cron.

[dentarg]

The cron job is configured at https://travis-ci.org/klubbdinmamma/klubbdinmamma.github.io/settings

[dentarg]

Hmm, I don't want to remove and exclude _data/facebook from git, I think they are good to keep around, makes for fast local builds (though the could easily be outdated, but then you can update them manually).

Then we make _plugins/remote_facebook_photos.rb always fetch fresh data from Facebook if run via cron on Travis by looking at TRAVIS_EVENT_TYPE.

[dentarg]

Re: the facebook app secret and ENV, Travis can encrypt files: https://docs.travis-ci.com/user/encrypting-files/, so it should be possible to use _config_secrets.yml on Travis

[dentarg]

Then we make _plugins/remote_facebook_photos.rb always fetch fresh data from Facebook if run via cron

We need to always fetch fresh data from facebook on Travis (i.e. deploying) if the repo can contain stale data.

[dentarg]

$ travis encrypt-file _config_secrets.yml --add
Detected repository as klubbdinmamma/klubbdinmamma.github.io, is this correct? |yes| y
encrypting _config_secrets.yml for klubbdinmamma/klubbdinmamma.github.io
storing result as _config_secrets.yml.enc
storing secure env variables for decryption

Make sure to add _config_secrets.yml.enc to the git repository.
Make sure not to add _config_secrets.yml to the git repository.
Commit all changes to your .travis.yml.

[dentarg]

working iteratively, pushing many commits would build up a big deploy backlog and the Facebook API might not like it?

Not a problem with Auto Cancellation: https://blog.travis-ci.com/2017-03-22-introducing-auto-cancellation