Add copy and copytree methods

[jayqi]

We should have copy and copytree methods for copying from one cloud path to another, similar to how shutil's functions work.

[genziano]

Hello, I was building a library for the same purpose, and I discovered this very nice one. I would like to contribute; is it ok if I pick this one up?

[jayqi]

Yes! Thank you for your interest and the offer to contribute! Let us know if you have any questions.

[pjbull]

That @genziano, that would be awesome. Just as a heads up, I think we may need two code paths:

(1) that uses the _move_file method on the client, which does a copy without transiting through the machine using cloudpath lib. (e.g., here is the implementaiton for S3). This is only guaranteed to work if the client on the CloudPath is the same client (since then the creds can access both buckets).

(2) that can work across cloud providers. This will likely need to do a download then upload and transit through the machine running cloudpathlib code.

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Also, there are few notes in the issue about contributing that may be useful while we haven't done full contributor instructions yet:
#25 (comment)

[genziano]

Great, I will work on it! And thanks for the tips.

I have one initial question: to which object should the methods copy and copytree belong? Or should they be functions in a submodule that replicates the shutil API?

[pjbull]

IMO on CloudPath makes the most sense. Usage would look like. @jayqi did you have other thoughts?

p1 = CloudPath("s3://b/file1.txt")

# copies the file from p1 to the passed path
p2 = p1.copy(CloudPath("s3://b/file2.txt"))

# str destination passes through to instantiation using the CloudPath factory on p1
p2 = p1.copy("s3://b/file2.txt")

# dir destination copies and keeps filename
p2 = p1.copy(CloudPath("s3://b/folder/"))

# copy on a dir raises error to use copytree if src is not a file
CloudPath("s3://b/folder/").copy("s3://b/folder2")

# copies the entire directory from folder1 to folder2
CloudPath("s3://b/folder/").copytree("s3://b/folder2")

[machielg]

would be nice to have this feature, is there a plan for releasing?

[pjbull]

This is being worked on in PR #142 now. @BenAsaf had mentioned he may be able to take a look at implementing in the near future.