[FEATURE] Support multiple var-files

[rkettelerij]

Currently levant only supports one -var-file argument. It's possible to overwrite variables in the variables file by providing one or more -var="k=v" arguments. It would be convenient to also support multiple -var-file arguments.

My use case is that I have one generic variables files and several application specific variable files. Therefore I'd like to do something like this:

./levant render -var-file=generic.yaml -var-file=specific.tf -var="job_name=myjob" mytemplate.nomad

Thus supply multiple -var-files where variable files are evaluated in the order in which they are specified on the command line. If a particular variable is defined in more than one variable file, the last value specified is effective. This is identical to the way Terraform handles multiple var-files.

[rkettelerij]

PR submitted: #180

[stevenscg]

Nice feature idea! I've run into this a few times myself. While I've been able to work around those cases, this would allow some de-duplication of some vars.