Support stated requirements

[jaraco]

I recently had a situation where I wanted to compare the dependencies installed in CI environments, where the deps installed are emitted in a compact form from tox:

python: freeze> python -m pip freeze --all
python: attrs==23.1.0,autocommand==2.2.2,black==23.3.0,build==0.10.0,click==8.1.3,coverage==7.2.6,docutils==0.20.1,fastjsonschema==2.17.1,filelock==3.12.0,inflect==6.0.4,iniconfig==2.0.0,jaraco.context==4.3.0,jaraco.functools==3.6.0,jaraco.path==3.5.0,jaraco.test==5.3.0,jaraco.text==3.11.1,jsonschema==4.17.3,jupyter_core==5.3.0,more-itertools==9.1.0,mypy==1.3.0,mypy-extensions==1.0.0,nbformat==5.8.0,packaging==23.1,path==16.6.0,pathspec==0.11.1,pip==23.1.2,pip-run @ file:///home/runner/work/pip-run/pip-run/.tox/.tmp/package/1/pip_run-0.1.dev1%2Bg21fa42e-0.editable-py3-none-any.whl#sha256=3367087b634015c70f2aa67fd6e6a9fc2657cd35f79aa3e6663ac4ae354f442b,platformdirs==3.5.1,pluggy==1.0.0,pydantic==1.10.8,Pygments==2.15.1,pyproject_hooks==1.0.0,pyrsistent==0.19.3,pytest==7.3.1,pytest-black==0.3.12,pytest-checkdocs==2.9.0,pytest-cov==4.0.0,pytest-enabler==2.1.1,pytest-mypy==0.10.3,pytest-ruff==0.0.6,ruff==0.0.269,setuptools==67.8.0,toml==0.10.2,traitlets==5.9.0,typing_extensions==4.6.0,wheel==0.40.0

I'd like to be able to copy that line (the output of pip freeze) and paste it into a command-line as the before or after to compare-requirements. Instead, I had to paste them into a file and then replace the commas with newlines, then run the compare, then delete the files.

I'd rather be able to do cmpreq 'attrs==23.1.0,autocommand==2.2.2,black==23.3.0,build==0.10.0,click==8.1.3,coverage==7.2.6,docutils==0.20.1,fastjsonschema==2.17.1,filelock==3.12.0,inflect==6.0.4,iniconfig==2.0.0,jaraco.context==4.3.0,jaraco.functools==3.6.0,jaraco.path==3.5.0,jaraco.test==5.3.0,jaraco.text==3.11.1,jsonschema==4.17.3,jupyter_core==5.3.0,more-itertools==9.1.0,mypy==1.3.0,mypy-extensions==1.0.0,nbformat==5.8.0,packaging==23.1,path==16.6.0,pathspec==0.11.1,pip==23.1.2,pip-run @ file:///home/runner/work/pip-run/pip-run/.tox/.tmp/package/1/pip_run-0.1.dev1%2Bg21fa42e-0.editable-py3-none-any.whl#sha256=3367087b634015c70f2aa67fd6e6a9fc2657cd35f79aa3e6663ac4ae354f442b,platformdirs==3.5.1,pluggy==1.0.0,pydantic==1.10.8,Pygments==2.15.1,pyproject_hooks==1.0.0,pyrsistent==0.19.3,pytest==7.3.1,pytest-black==0.3.12,pytest-checkdocs==2.9.0,pytest-cov==4.0.0,pytest-enabler==2.1.1,pytest-mypy==0.10.3,pytest-ruff==0.0.6,ruff==0.0.269,setuptools==67.8.0,toml==0.10.2,traitlets==5.9.0,typing_extensions==4.6.0,wheel==0.40.0' 'other'