While looking for creating a juliahub import script, I had to look on
how other packages were downloading repositories, and some things could
be factorised. I plan to use this new function for the juliahub importer
I still need to experiment with it a bit, ensure that all cases are
covered, but here's a preliminary patch to get some feedback.
I believe such could also be done for other VCS, as Katherine Cox-Buday
probably had in mind when writing the go importer.
The code to download and hash from hg is already there in the cran
"download" helper. Maybe we can also add some options to the original
hg-fetch function from guix/build/hg.scm to factorize hg directly ?