Force sig file extension to be sig or sig.gz

[mr-eyes]

Since the user has the power to sig rename or generates signatures without .sig or .sig.gz extension. And since the zipStorage implementation expects .sig or .sig.gz extension as per

sourmash/src/sourmash/index/__init__.py

Lines 623 to 624 in 7b55c52

	if filename.endswith('.sig') or \
	filename.endswith('.sig.gz') or \

Enforcing/unifying signature extensions to be .sig or .sig.gz can reduce some errors.

[mr-eyes]

Maybe I am getting it wrong? due to the traverse_yield_all after that?
@luizirber @ctb

[ctb]

Hi @mr-eyes I don't understand -

All of the internal code reads and writes .sig/.sig.gz file names by default and by convention. The user can specify a different file extension if they want and it will be read appropriately, but only .sig and .sig.gz files will be auto-discovered on traversal unless -f is specified.

So, for example, if a directory has a bunch of .sig.gz files under it, and you point sourmash at the directory it will load all those files and no more, unless you specify -f. Same with a zip file.

[ctb]

oh! perhaps you mean we should require it all the time?

I don't recall why I thought it was a good idea Back When, and it causes some interesting problems and weird behavior (see comments about 'traverse_all' in #1849). But it isn't our convention and I don't think it causes too many problems in the code. I don't have any real problem with changing it but it would have to be part of a major version bump (at least 1, if not 2) because of semantic versioning. I'm tempted to say that we should just leave it.

[mr-eyes]

oh! perhaps you mean we should require it all the time?

Yes exactly!

I don't have any real problem with changing it but it would have to be part of a major version bump (at least 1, if not 2) because of semantic versioning. I'm tempted to say that we should just leave it.

Ok then, I labeled it to the next major version for now :)