Move unpack_file_url() out of download.py

[cjerdonek]

As a follow-on to PR #6859, unpack_file_url() and the functions it depends on should be moved out of download.py into a new module IMO since this function doesn't do any downloading or require network access -- just copying / unpacking on the file system:

pip/src/pip/_internal/download.py

Lines 939 to 950 in 1de04eb

	def unpack_file_url(
	link, # type: Link
	location, # type: str
	download_dir=None, # type: Optional[str]
	hashes=None # type: Optional[Hashes]
	):
	# type: (...) -> None
	"""Unpack link into location.
	If download_dir is provided and link points to a file, make a copy
	of the link file inside download_dir.
	"""

Does anyone have any thoughts on the name of the new module? I think it can probably be inside utils. It is shutil-like (needing things like shutil.copytree()) and so feels higher-level than utils/filesystem.py.

Doing this will also let us remove wheel.py's import dependency on download.py.

This is also related to issue #6813 ("Breakout pip._internal.download to a pip._internal.network sub-package").

Posted in its original form by @cjerdonek in #6859 (comment)

[cjerdonek]

Functions in misc.py like unpack_file(), untar_file(), and unzip_file() would probably be good moved to this new module, too:

pip/src/pip/_internal/utils/misc.py

Lines 727 to 732 in 1de04eb

	def unpack_file(
	filename, # type: str
	location, # type: str
	content_type, # type: Optional[str]
	link # type: Optional[Link]
	):

Maybe unpacking.py?

[ivenk]

I will try and submit a PR later on.

[chrahunt]

After looking at it more, I think it would be better to move the networking/http-specific stuff out of download and into something in utils (or another top-level folder under which we can split up networking). unpack_file_url and unpack_http_url are essentially the same function - moving them away from each other may make it harder to see that and refactor.

[cjerdonek]

Since you were able to remove wheel.py's dependence on download.py without moving unpack_file_url(), I'm okay with closing this issue.