.. after upgrading a couple of packages

- change references to temporary branches (e.g., "release-*" and
  "publish") to point to the 'main' branch
- add --branch=BRANCH_NAME option to the nox session so that
  one can pass in a target branch to make all references point to
- run "fix-branch-references" as the first pre-commit hook
  as it fails the fastest
- bug fix: allow dots in branch references (e.g., "release-0.1.0")

- dependencies used to run the Jupyter Lab environment that are not
  required by the `urban-meal-delivery` package itself are put into
  an installation extra called "research"
- this allows to NOT install the requirements, for example, when
  testing the package in an isolated environment

- run "format" and "lint" separately
  => remove the nox session "pre-commit"
- execute the entire "test-suite" before merges
  + rename "pre-merge" into "test-suite"
  + do not "format" and "lint" here any more
  + do not execute this before pushes
    * allow branches with <100% test coverage to exist on GitHub
      (they cannot be merged into 'main' until 100% coverage)
    * GitHub Actions executes the test suite

- many *.py and *.ipynb files will contain links to resources on
  GitHub or nbviewer that have branch references in them
- add a pre-commit hook implemented as the nox session
  "fix-branch-references" that goes through these files and
  changes all the branch labels to the current one

- some glob patterns in .gitignore were not correctly expanded
- adapt the exclude logic to focus on the start of the excluded paths

- use Alembic to migrate the PostgreSQL database
  + create initial migration script to set up the database,
    as an alternative to db.Base.metadata.create_all()
  + integrate Alembic into the test suite; the db_engine fixture
    now has two modes:
    * create the latest version of tables all at once
    * invoke `alembic upgrade head`
    => the "e2e" tests are all run twice, once in each mode; this
       ensures that the migration scripts re-create the same database
       schema as db.Base.metadata.create_all() would
    * in both modes, a temporary PostgreSQL schema is used to create the
      tables in
    => could now run "e2e" tests against production database and still
       have isolation
- make the configuration module public (to be used by Alembic)
- adjust linting rules for Alembic

- use SQLAlchemy (and PostgreSQL) to model the ORM layer
- add the following models:
  + Address => modelling all kinds of addresses
  + City => model the three target cities
  + Courier => model the UDP's couriers
  + Customer => model the UDP's customers
  + Order => model the orders received by the UDP
  + Restaurant => model the restaurants active on the UDP
- so far, the emphasis lies on expression the Foreign Key
  and Check Constraints that are used to validate the assumptions
  inherent to the cleanded data
- provide database-independent unit tests with 100% coverage
- provide additional integration tests ("e2e") that commit data to
  a PostgreSQL instance to validate that the constraints work
- adapt linting rules a bit

... after upgrading:
- flake8-plugin-utils
- sphinx

- add the following file:
  + src/urban_meal_delivery/_config.py
- a config module is created holding two sets of configurations:
  + production => against the real database
  + testing => against a database with test data
- the module is "protected" (i.e., underscore) and imported at the
  top level via a proxy-like object `config` that detects in which of
  the two environments the package is being run

- only support Python 3.8 in the project
  as GitHub Actions has no 3.9 in its base image
- re-order some sessions so that the order in
  `poetry run nox --list` is more intuitive
- add extensive documentation to the noxfile.py module
- add more whitespace to noxfile.py to make it easier to read
- add generic maintainance tasks:
  + "init-project" => set up all pre-commit hooks
  + "clean-pwd" => ~ `git clean -X` with minor exceptions
- upgrade isort to 5.3.0

- use sphinx to document the developed package
- create a nox session "docs" that builds the docs
- include a skeleton in the docs/ folder
  + how to install the package
  + how to use nox
  + license

- use xdoctest to validate all code snippets in docstrings
- add xdoctest to the nox session "test"

- add a nox session "safety"

- for tests/ and the noxfile.py, type annotations are not strictly
  enforced any more
  + this simplifies the way test cases and nox sessions are written
  + for many pytest fixtures, no types are available via a public API
- put fixtures inside the classes the corresponding test cases are
  grouped in

- add the following file:
  + src/urban_meal_delivery/console.py => click-based CLI tools
  + tests/test_console.py => tests for the module above
- add a CLI entry point `umd`:
  + implement the --version / -V option
    to show the installed package's version
  + rework to package's top-level:
    * add a __pkg_name__ variable to parameterize the package name
  + add unit and integration tests
- fix that pylint cannot know the proper order of imports in the
  isolated nox session

- add pre-commit and pre-merge hooks:
  + run `poetry run nox -s pre-commit` on staged *.py files
  + run common pre-commit hooks for validations that could not be
    achieved with tools in the develop environment so easily
  + run `poetry run nox -s pre-merge` before merges and pushes
- implement the "pre-commit" and "pre-merge" sessions in nox
  + include a little hack to deal with the positional arguments
    passed by the pre-commit framework
- provide more documentation on the nox sessions

- use pytest as the base, measure coverage with pytest-cov
  + configure coverage to include branches and specify source locations
  + configure pytest to enforce explicit markers
- add a package for the test suite under tests/
- add a `__version__` identifier at the package's root
  + it is dynamically assigned the version of the installed package
  + the version is PEP440 compliant and follows a strict subset of
    semantic versioning: x.y.z[.devN] where x, y, z, and N are all
    non-negative integers
  + add module with tests for the __version__
- add a nox session "test" that runs the test suite
- use flake8 to lint pytest for consistent style

- use flake8 as the main and pylint as the auxiliary linter
- install flake8 with the following plug-ins:
  + flake8-annotations => enforce type annotations for functions/classes
  + flake8-black => ensure black would not make any changes
  + flake8-expression-complexity
  + wemake-python-styleguide, which packages the following:
    * darglint         * flake8-bandit         * flake8-broken-line
    * flake8-bugbear   * flake8-commas         * flake8-comprehensions
    * flake8-debugger  * flake8-docstrings     * flake8-eradicate
    * flake8-isort     * flake8-rst-docstrings * flake8-string-format
    * flake8-quotes    * pep8-naming
- configure flake8 & friends in a rather explicit and strict way
- isort needed to be downgraded to ^4.3.21 due to a conflict with
  pylint and wemake-python-styleguide:
  + provide TODO's to remove the parts that "fix" isort
- use mypy for static type checking
- add a nox session "lint" that runs flake8, mypy, and pylint
- lint all source files

- (auto-)format code with:
  + autoflake => * remove unused imports and variables
                 * remove duplicate dict keys
                 * expand star imports
  + black => enforce an uncompromising code style
  + isort => enforce a consistent import style
             (complying with Google's Python Style Guide)
- implement the nox session "format" that runs all these tools
- add the following file:
  + setup.cfg => holds configurations for the develop tools

- set up skeletons for all planned nox sessions
- provide a base configuration for all nox sessions
- create two utility functions:
  + _begin() => run commands common to all sessions
  + _install_packages() => install dependencies in nox sessions
                           respecting the versions pinned in poetry.lock
- add the following file:
  + noxfile.py

- add the following files:
  + .gitignore => ignore poetry's and pyenv's artifacts
  + LICENSE.txt => MIT license as the project is scientific research
  + README.md => rough description of the project
  + poetry.lock
  + pyproject.toml
  + src/urban_meal_delivery/__init__.py => source code package
- use a "src" layout structure:
  + ensure that pytest runs the tests against a packaged and pip
    installed version of the source code, not the *.py files in the
    project directory
  + more info: https://hynek.me/articles/testing-packaging/