deprecate: using Dvcfile is confusing and maybe should be deprecated

[dashohoxha]

The command dvc pipeline show --ascii <targets> is supposed to work without any targets as well (as explained by the help message: dvc pipeline show --help). However it complains instead about the absence of Dvcfile:

WARNING: assuming default target 'Dvcfile'.
ERROR: failed to show pipeline for 'Dvcfile' - 'Dvcfile' does not exist.

This is confusing for the users. Without any targets, it should show all the pipelines available (as the help message says). This would be more reasonable than searching for a "Dvcfile".

Moreover, I think that using Dvcfile as a default target should be deprecated in general. It is much better to fail and ask for a .dvc file, when it is missing, than to assume that the default is Dvcfile.

[dashohoxha]

Related: #2392

[pared]

Some context

[efiop]

Moreover, I think that using Dvcfile as a default target should be deprecated in general. It is much better to fail and ask for a .dvc file, when it is missing, than to assume that the default is Dvcfile.

Dvcfile is similar to Makefile and is used for other commands like dvc repro to provide a feature that allows you to run your command without a specific target, so the creator of the project could decide which targets should be reproduced by default. It is also useful when you have a dedicated directory for your pipeline step (e.g. https://github.com/nestauk/gateway_to_cookies/tree/master/pipe). I don't think that pipeline show issue is a good enough reason to abandon Dvcfile's in general, the reasons behind pipeline show behaviour are discussed #2392 . Also, removing Dvcfile would break backward compatibility. Closing this for now.

[shcheklein]

I think the help message should be updated. It looks like an UI bug to me at the very least.

[dashohoxha]

Dvcfile is similar to Makefile

@efiop Everything that you say about Dvcfile may be right, but IMHO the analogy with a Makefile is broken. I would love it if Dvcfile was similar to Makefile (or Dockerfile).

[efiop]

@shcheklein It should be a part of #2392 , no need to keep a duplicate issue.

[efiop]

@dashohoxha Sure, it is not a 1to1 conformity, I'm just saying that the idea behind a default file name is a similar one to both Makefile and Dockerfile.

[efiop]

Closing in favor of #2392