build: Require an explicit fetch stage is not working

[ravanelli]

Seems we have a regression for https://github.com/coreos/coreos-assembler/pull/1379

Running cosa build ostree or cosa build without cosa fetch is not getting the fatal "Must fetch before building anymore

[Regis-Caelum]

Hey, @ravanelli. I would like to work on this one. Could you give me some pointers on how to get started

[ravanelli]

Hey @Regis-Caelum, first, thanks for working on it.

Since this issue was opened a while ago, we need to make sure it still an issue. Here is the doc about how to build FCOS, in the Performing a build phase we have 2 steps :cosa fetch and cosa build. You need to run cosa fetch first or cosa build will fail, the issue here is: if you run cosa build without cosa fetch it is not warning you about it as described in https://github.com/coreos/coreos-assembler/pull/1379