[RFC] Travis: Use container-based infrastructure where possible.

[fwalch]

Information on the container-based infrastructure is here.

See here for a test build. The failing job is the OS X deps64 build (because OS X is not enabled on my fork). If you look at the job detail pages, you'll see the differences between the old (sudo: true) and the new (sudo: false) builds.

There might be a problem with the OS X build (travis-ci/travis-ci#2957), but unfortunately I have no way to test this. So I'd suggest just merging this and reverting if it doesn't work out.

To do: try to activate caching for the repositories that most of these jobs clone (neovim/neovim, neovim/doc, ...). Edit: I'd actually leave that for a later PR; if this doesn't work with OS X, it doesn't make sense to continue.

[justinmk]

👍 can vimpatch-report also use a container?

[justinmk]

compared to https://travis-ci.org/neovim/bot-ci/builds/45955949 the new container builds actually seem to be about 5% slower.

but if we enable caching, then that will be a big help.

[fwalch]

👍 can vimpatch-report also use a container?

Yes, it already does. The containerized builds are enabled by default (sudo: false).

compared to https://travis-ci.org/neovim/bot-ci/builds/45955949 the new container builds actually seem to be about 5% slower.

The nightly build should be a bit faster.

Some jobs failed!? It worked in the test build on my fork.. also, the failed jobs don't even use the container builds.

[justinmk]

https://lint.travis-ci.org/neovim/bot-ci says:

in matrix.include.compiler section: illegal value gcc-4.9, defaulting to gcc
in matrix section: unexpected key sudo, dropping

[justinmk]

reverting until travis-ci/travis-ci#2957 is resolved