https://github.com/tectonic-typesetting/tectonic/issues/53 has been fixed

Otherwise conda cannot be found by GitLab CI.

The --cleanup flag is necessary to build multiple images in one
container. But that flag removes everything that's not in
the vanilla kaniko image.

Use the first parent commit for changed files as fallback

See merge request omegacen/ci-templates!55

v5

Closes #8

See merge request omegacen/ci-templates!53

The CI job token has limited access to the API; cf.
https://docs.gitlab.com/ee/ci/jobs/ci_job_token.html

Otherwise, you cannot disable all CI jobs and enable just one.

Also, remove run/skip variables from MM and AST jobs. These do
not make sense there.