Automatically detect if no programming language is present to show overview in data-only repository

[quazar-omega]

Hi!

Summary 💡

Even in repositories where there are no programming languages (e.g. https://github.com/LemmyNet/lemmy-ansible) but only data/configuration, by default you get this:

Error: Could not find any source code in this repository

Maybe in such cases it shouldn't ignore non-programming languages and produce an error output, but fall back to the other most prevalent language.

Motivation 🔦

Related to #1208.
I didn't know right away how to make YAML appear and I was confused because I saw that it was supported as a language, then I found that issue and understood, but it wasn't very intuitive.

Maybe it is also worth reopening that issue, I think an improvement there could be to enrich this error message with suggestions, like:

Error: Looking for programming language source code, but couldn't find any in this repository
       You can add the option `-T data/markup/...` to show the repository overview regardless

Or even better, based on the content of the repository, it could suggest which argument to provide to the -T option, though, if it's able to do that, it would probably be better to just do it without further user intervention, which falls back into this issue (idk, I'm confused because I'm not aware of all the possibilities)

[spenserblack]

Semi-related to #1305. Detectable files can be controlled with a configuration, and also a summary can be generated with different options to get different results.

[quazar-omega]

So do you think that the option should just be better represented?
IMO, even just a more verbose error message would suffice as I feel like it's more of a discoverability issue and the current error text sounds a bit misleading at first sight

[spenserblack]

Yeah, I do think updating the error message is a great start. I was kind of just hinting at how this could be handled in the future and investigating the idea of automatically removing filters if nothing is detected.

[quazar-omega]

Oh, I see now!