[Feature Request] Support using .yml file extension instead of .yaml

[KamWithK]

🚀 Feature Request

In a lot of projects, the .yml file extension is used instead of .yaml as it is slightly more concise and I've seen and used it more often.
Hence, would it be possible to either find and use both .yml and .yaml files or to have a simple parameter which switches between whether to look for .yaml or .yml?

Motivation

In a lot of projects, the .yml file extension is used instead of .yaml as it is slightly more concise and I've seen and used it more often.
In my project, we have a large number of configuration files (not just for Hydra) and the .yml file extension has already been chosen.
Now that I'm implementing Hydra into our model creation and training code, it is frusturating to have to see that half my configuration uses .yml and the other half .yaml.
The issue was previouslly raised and closed here due to difficulty checking for two file types.
BUT, if instead of checking for both there was a parameter declairing which was used it might make it easier to deal with

[omry]

Thanks for your suggestion.
This is unfortunately more complicated than it seems:

1. This cannot be configured in the config files because how would that file be found?
2. Hydra itself, as well as Hydra plugins and installed frameworks may be accessing config files they installed, changing the extension will break all of them.

Overall I think the utility from this is very low and it's not worth the added complexity and implementation effort.
#408 is a similar feature request to support json files that I am keeping open (yaml is a superset of json so this is really about supporting another file extension).
The chances of it being implemented are low but I am not completely ruling it out yet.

Closing this one, feel free to continue discussing here.

[ndrwnaguib]

Wouldn't supporting .yml along with .yaml files be a wider scope of interoperability. I am not motivating to use yml instead, but supporting it too. If you are convinced, I will be happy to implement it with some guidance tips.

[omry]

Read my reasons above and in #408 to only support .yaml for config file extension.
That decision is made.