export to requirements.txt without freezing version

[gsemet]

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

It would be really helpful to be able to export to requirements.txt without freezing the version, and keeping the markers.
This is an important feature in order to support "libraries", where you want to inject the content of requirements.txt into setup.py 's install_requires. This is what PBR does, and with pipenv I was used to keep requirements.txt in sync with Pipfile. I have written a little tool for that: pipenv-to-requirements.

Now I am trying to migrate to poetry, and facing the same issue: I want my prod packages to be added into install_requires automatically, or keep a requirements.txt into my packages, so that when my packages will be installed by pip, it will install its dependencies automatically.

So, what I need when I am building a library is to read tool.poetry.dependencies from pyproject.toml and generate a requirements.txt without freezeing and with the markers.

Can't acheive that with poetry export (it freeze the version and loose the markers), neither with dephell. I have no pbl submitting this feature in poetry if you accept it :)