Allow to use different hashing algorithms

[Xarthisius]

Rationale

I'm trying to use pooch to manage/fetch data stored in external data repositories. All of them provide some sort of checksum, unfortunately it's not always SHA256. Ideally I'd like to generate pooch's registry file using hashes obtained directly from a given data repository. However, I need to be able to use proper hashing algorithm for data verification.

Implementation

Extend registry format from:

name hash url

to

name alg:hash url

Whenever old format registry is detected (i.e. : is not present in hash) sha256: is prepended to the hash automatically, which ensures backward compatibility.

TODO

• Update docs

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[leouieda]

@Xarthisius thank you for taking the time to implement this! 🎉 I was actually just thinking of this a couple of days ago. I left a few comments (mostly minor) that need to be addressed before moving forward. Let me know if you need any feedback/help/opinion.

[leouieda]

Would this be a useful function to have in pooch/core.py? The same code is used in Pooch.__init__.

[leouieda]

@Xarthisius thanks for making those changes. Looks like this is almost good to go! Only need some text in the docstrings about specifying the hash algorithms and that one comment about the add_hash_algs function.

If you have the time, it would also be nice to have a short section in doc/usage.rst page about specifying different hashes.

[leouieda]

It would also be nice to have at least 1 test using a different hash algorithm.

[Xarthisius]

@leouieda I believe I addressed all the comments. I'd appreciate a 2nd review.

[leouieda]

@Xarthisius looks good to me 👍 Merging this in!

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