`__truediv__` shouldn't mutate the URL

[ksonj]

I'm a big fan of being able to do

>>> p = furl.furl("https://example.com")
>>> p / "some-path"
furl("https://example.com/some-path")

What really freaks me out though, is that this operation mutates p:

>>> p
furl("https://example.com/some-path")

To be consistent with pathlib.Path, this should produce a new object and leave p be:

>>> p = furl.furl("https://example.com")
>>> p / "some-path"
furl("https://example.com/some-path")
>>> p
furl("https://example.com")

So what I am suggesting is to remove the equivalence furl.add(s) == furl.__truediv__(s).
If a shorthand for mutating the url in place is needed, we should use __itruediv__ (i.e. p /= "some-path") instead. So:

>>> p = furl.furl("https://example.com")
>>> p / "some-path"  # Returns furl
furl('https://example.com/some-path')
>>> p
furl('https://example.com')
>>> p /= "some-path"  # Returns None
>>> p
furl('https://example.com/some-path')

I am volunteering to prepare a PR, if this is approved of.

[Ansgar Grunseid]

I agree.

This is an oversight in the API. __trudiv__ should not mutate the original
furl object.

Usage like

>>> from furl import furl
>>> f = furl('http://www.google.com/')
>>> p1 = f / '11111'
>>> p2 = f / '22222'
>>> f.url, p1.url, p2.url
'http://www.google.com/', 'http://www.google.com/11111', 'http://www.google.com/22222'

should be accomodated and encouraged.

I am volunteering to prepare a PR, if this is approved of.

Awesome. A pull request to resolve this is most welcome. Let me know how I can
help!

[Ansgar Grunseid]

This change shipped in furl v2.0.0. Upgrade with

pip install furl --upgrade

Thank you again, @ksonj. Don't hesitate to let me know if there's anything I can
do for you.