Removal of master branch in poetry-core on June 1, 2023 #6741

The main branch of poetry-core was renamed from master to main in May 2022. Since this broke some packages explicitly referencing master, it was decided to copy the main branch into master branch to not break those usages.

As master is not updated from main, and it is confusing to keep both branches around, there's no point keeping master indefinitely.

So this issue acts as a deprecation notice for usages of master branch of poetry-core, as we are planning to delete the branch on June 1, 2023.

This change will impact packages that use git references when defining poetry-core as a build-system, for instance by doing:

[build-system]
requires = ["poetry-core @ git+https://github.com/python-poetry/poetry-core.git@master"]
build-backend = "poetry.core.masonry.api"

Once master branch is removed, any package still referencing master branch as their build system will not be installable. Note that using a moving git branch for the build system on published packages is a highly discouraged practice, since:

• update to branches could break usages at any moment, as they represent a development version of the project, and not official releases
• branches are not immutable, and can be deleted in git

If you are a package maintainer and are referencing poetry-core by using master branch from the git repository (or any other branch, for what it's worth), it is highly recommended to update the build system of the package to rely on versions published to PyPI, for instance:

[build-system]
requires = ["poetry-core"]
build-backend = "poetry.core.masonry.api"

or, if you rely on features implemented in specific versions of poetry-core, by defining a lower bound, for instance:

[build-system]
requires = ["poetry-core>=1.2.0"]
build-backend = "poetry.core.masonry.api"