Include "via" information, like "pip-compile"

When pip-compile creates a requirements.txt, it will include a "via" line for each requirement: this line defines the rationale for why the requirement was included, such as "via -r requirements.in" or "via requests"

poetry has access to this information, it would be cool if it could be propagated to the exported requirements.txt file.

Example from pip-compile:

#
# This file is autogenerated by pip-compile with python 3.10
# To update, run:
#
#    pip-compile
#
certifi==2021.10.8
    # via requests
charset-normalizer==2.0.12
    # via requests
idna==3.3
    # via requests
requests==2.27.1
    # via -r requirements.in
urllib3==1.26.9
    # via requests

This would provide two benefits:

• It could make it easier to port from pip-compile, since generated requirements.txt files between it and poetry-plugin-export would be more similar
  • Selfishly, I'm mostly looking for this for my pip-compile-cross-platform project :)
• It removes a step from debugging: the associated poetry.lock file doesn't have to be located and perused, as the information is all available in the one requirements.txt file.

Start by tracing the poetry-plugin-export path that produces requirements.txt and compare its output with pip-compile's "via" comments. Review how dependency relationships are represented in poetry.lock, then verify that exported requirements include rationale comments such as "via requests" and "via -r requirements.in" without changing dependency versions.