We now build a docker base container based on debian sid (where the very
latest packages are available). That base container is updated once a
month, or whenever travis-build.Dockerfile or debian/control change, but
re-used for subsequent travis runs. While the initial build might take
up to 15 minutes, subsequent builds typically run in a minute or two.
All the different steps that we run on travis are now factored into
separate scripts in the travis/ directory.
Switching to docker should also help with issue #2174.
This is useful for third-party scripts which require certain features
and want to error out cleanly when they are run with an old i3 version.
Additionally, i3 --version might be different from what’s actually
running (an old version of the binary), so i3-msg -t get_version will be
the best way to figure out the i3 version you are actually running from
this commit on.
