Adds eland-docs repo to conf.yaml and alias to doc_build_aliases.sh

[szabosteve]

This PR adds a new repository (eland-docs) to the conf.yaml file and a build alias to the doc_build_alias.sh file.

Depends on elastic/elasticsearch-eland-docs#4. Please merge that PR first

[lcawl]

I created elastic/elasticsearch-eland-docs#4 to fix the resolution of the shared attributes. Please merge that PR before you merge this one.

I also added the "single: 1" option to the conf.yaml and the "--single" option to the build alias in this PR, since that makes it a single page to match what's done for other clients.

[szabosteve]

@elasticmachine test this please

[lcawl]

@elasticmachine run elasticsearch-ci/docs rebuild

[lcawl]

I can replicate this build error on my local machine, by running the ./docs/build_docs --all --target_repo git@github.m:elastic/built-docs.git --open command:

09:49:36 INFO:build_docs: - eland Client: Building master...
09:49:36 INFO:build_docs: - eland Client: Building 7.x...
09:49:36 INFO:build_docs: - eland Client: Finished master
09:49:36 INFO:build_docs: - eland Client: Finished 7.x
09:49:36 INFO:build_docs:couldn't update version at lib/ES/Book.pm line 383.

The error goes away and the docs build is successful if I (A) remove either master or 7.x from the list of branches, or (B) remove the "single: 1" option.

@nik9000 This seems like a bug to me, since --single is defined as "Generate a single HTML page, instead of a chunking into a file per chapter" but that shouldn't mean that you can have multiple branches of that single page.

[szabosteve]

@lcawl @nik9000
In the meantime, I removed master from the list of branches as the valid documentation will be in 7.x anyway. I won't merge this until Nik can have a look.
Thanks to both of you!

[nik9000]

I've reproduced the issue locally and will fix it. I'm not sure what is causing it yet, but I'll fix it!

[nik9000]

I also added the "single: 1" option to the conf.yaml and the "--single" option to the build alias in this PR, since that makes it a single page to match what's done for other clients.

I believe the bug that we have is that single page books can't have more than one version. I'm not sure why that is, but eland would be the first book that does.

For what it is worth lots of our clients use standard chunking: Java, PHP, Javascript, .NET, Ruby. The ones that just link off to their "native" docs like python and perl do not. I'm not sure what eland plans to do.