Commits to master should run all builds in CI matrix

[asfimport]

After ARROW-2083, we are only running builds related to changed components with each patch in Travis CI and Appveyor.

The problem with this is that when we merge patches to master, our Travis CI configuration (implemented by ASF infra to help alleviate clogged up build queues) is set up to cancel in-progress builds whenever a new commit is merged.

So basically we could have in our timeline:

• Patch merged affecting C++, Python

• Patch merged affecting Java

• Patch merged affecting JS

  So when the Java patch is merged, any in-progress C++/Python builds will be cancelled. And if the JS patch comes in, the Java builds would be immediately cancelled.

  In light of this I believe on master branch we should always run all of the builds unconditionally

Reporter: Wes McKinney / @wesm
Assignee: Antoine Pitrou / @pitrou

PRs and other links:

• GitHub Pull Request #1634

_{Note: This issue was originally created as ARROW-2192. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
I see... So we should be able to decide this based on the environment variables exported by Travis-CI :

https://docs.travis-ci.com/user/environment-variables/#Convenience-Variables

[asfimport]

Wes McKinney / @wesm:
I think the Appveyor builds are OK as is (they will always run), but we can address them further in the future if need be

[asfimport]

Wes McKinney / @wesm:
Issue resolved by pull request 1634
#1634