Warn or error on mis-cased Procfile

[edmorley]

On Heroku currently, Codon outputs the following warning if an app has a procfile rather than the correctly named Procfile:

~     Mis-cased procfile detected; ignoring.
~     Rename it to Procfile to have it honored.

We should add something similar to this buildpack.

We should likely also make this an error rather than a warning.

[edmorley]

An example of a lower-cased procfile causing confusion even on classic (where there is already a warning):
https://heroku.support/1414816

As such it seems either an error or else accepting both capitalisations might be preferable?

[schneems]

accepting both capitalisations might be preferable?

Seems good. We could downcase everything so PrOcFiLe would be accepted as well.

Kick it up a notch: When there's no match output the closest 3 Levenshtein distance filenames

[edmorley]

I've also seen cases of Procfile.txt - might be worth checking for that too. (I think on Windows the context menu "New -> Text document" combined with Windows defaulting to hiding file extensions for known file types, is what leads to that being common - I've seen it for various Python related files too.)

[Malax]

I think we're all on the same page here, but just to clarify: we're talking about erroring after passing detection with misspelled Procfile and not about allowing anything else than Procfile, correct?

[edmorley]

I would be in favour of erroring rather than anything else, yeah.