Rework the automation for generating the scripts

.github/workflows/check.yml

@@ -0,0 +1,49 @@
+name: Check Scripts
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  correctly-generated:
+    name: "are correctly generated"
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+    - run: pip install nox
+
+    - run: nox -s generate
+    - name: Check regenerated scripts vs what is generated by automation.
+      run: git diff --exit-code
+
+  work-as-advertised:
+    name: "work as advertised"
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+    - run: pip install nox
+
+    # Install supported Python versions
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 2.7
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.5
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.6
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.7
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.8
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.9
+
+    # Check that the scripts work.
+    - run: nox -s check

.gitignore

@@ -1,3 +1,4 @@
 /.nox/
 /venv/
 __pycache__/
+.web_cache/

README.md

@@ -0,0 +1,72 @@
+# get-pip.py
+
+`get-pip.py` is a bootstrapping script that enables users to install pip,
+setuptools, and wheel in Python environments that don't already have them. You
+should not directly reference the files located in this repository and instead
+use the versions located at <https://bootstrap.pypa.io/>.
+
+## Usage
+
+```console
+$ curl -sSL https://bootstrap.pypa.io/get-pip.py -o get-pip.py
+$ python get-pip.py
+```
+
+Upon execution, `get-pip.py` will install `pip`, `setuptools` and `wheel` in
+the current Python environment.
+
+It is possible to provide additional arguments to the underlying script. These
+are passed through to the underlying `pip install` command, and can thus be
+used to constraint the versions of the packages, or to pass other pip options
+such as `--no-index`.
+
+```console
+$ python get-pip.py "pip < 21.0" "setuptools < 50.0" "wheel < 1.0"
+$ python get-pip.py --no-index --find-links=/local/copies
+```
+
+### get-pip.py options
+
+This script also has it's own options, which control which packages it will
+install.
+
+- `--no-setuptools`: do not attempt to install `setuptools`.
+- `--no-wheel`: do not attempt to install `wheel`.
+
+## Development
+
+You need to have a [`nox`](https://nox.readthedocs.io/) available on the CLI.
+
+### How it works
+
+`get-pip.py` bundles a copy of pip with a tiny amount of glue code. This glue
+code comes from the `templates/` directory.
+
+### Updating after a pip release
+
+If you just made a pip release, run `nox -s update-for-release -- <version>`.
+This session will handle all the script updates (by running `generate`), commit
+the changes and tag the commit.
+
+IMPORTANT: Check that the correct files got modified before pushing. The session
+will pause to let you do this.
+
+### Generating the scripts
+
+Run `nox -s generate`.
+
+## Discussion
+
+If you run into bugs, you can file them in our [issue tracker].
+
+You can also join `#pypa` or `#pypa-dev` on Freenode to ask questions or
+get involved.
+
+[issue tracker]: https://github.com/pypa/get-pip/issues
+
+## Code of Conduct
+
+Everyone interacting in the get-pip project's codebases, issue trackers, chat
+rooms, and mailing lists is expected to follow the [PSF Code of Conduct].
+
+[PSF Code of Conduct]: https://github.com/pypa/.github/blob/main/CODE_OF_CONDUCT.md

noxfile.py

@@ -1,9 +1,94 @@
 import os
+import textwrap
+from pathlib import Path
 
 import nox
 
+nox.options.sessions = ["check", "generate"]
 
-@nox.session(python=['2.7', '3.7'])
-def tests(session):
-    session.install('pytest')
-    session.run('pytest')
+
+# Keep versions in sync with .github/workflows/check.yml
+@nox.session(
+    python=["2.6", "2.7", "3.2", "3.3", "3.4", "3.5", "3.6", "3.7", "3.8", "3.9"]
+)
+def check(session):
+    """Ensure that get-pip.py for various Python versions, works on that version."""
+
+    # Find the appropriate get-pip.py file
+    public = Path(".")
+    locations = [
+        public / session.python / "get-pip.py",
+        public / "get-pip.py",
+    ]
+    for location in locations:
+        if location.exists():
+            break
+    else:  # AKA nobreak
+        raise RuntimeError("There is no public get-pip.py")
+
+    # Get rid of provided-by-nox pip
+    session.run("python", "-m", "pip", "uninstall", "pip", "--yes")
+    # Run the get-pip.py file
+    session.run("python", str(location))
+    # Ensure that pip is installed
+    session.run("python", "-m", "pip", "--version")
+    session.run("pip", "--version")
+
+
+@nox.session
+def generate(session):
+    """Update the scripts, to the latest versions."""
+    session.install("packaging", "requests", "cachecontrol[filecache]")
+
+    session.run("python", "scripts/generate.py")
+
+
+@nox.session(name="update-for-release")
+def update_for_release(session):
+    """Automation to run after a pip release."""
+    allowed_upstreams = [
+        "[email protected]:pypa/get-pip.git",
+        "https://github.com/pypa/get-pip.git",
+    ]
+
+    if len(session.posargs) != 1:
+        session.error("Usage: nox -s update-for-release -- <released-pip-version>")
+
+    release_version, = session.posargs
+
+    session.install("release-helper")
+    session.run("release-helper", "version-check-validity", release_version)
+    session.run("release-helper", "git-check-tag", release_version, "--does-not-exist")
+    session.run("release-helper", "git-check-remote", "upstream", *allowed_upstreams)
+    session.run("release-helper", "git-check-branch", "master")
+    session.run("release-helper", "git-check-clean")
+
+    # Generate the scripts.
+    generate(session)
+
+    # Make the commit and present it to the user.
+    session.run("git", "add", ".", external=True)
+    session.run(
+        "git", "commit", "-m", f"Update to {release_version}", external=True
+    )
+    session.run("git", "show", "HEAD", "--stat")
+
+    input(textwrap.dedent(
+        """\
+        **********************************************
+        * IMPORTANT: Check which files got modified. *
+        **********************************************
+
+        Press enter to continue. This script will generate a signed tag for this
+        commit and push it -- which will publish these changes.
+        """
+    ))
+
+    session.run(
+        # fmt: off
+        "git", "tag", release_version, "-m", f"Release {release_version}",
+        "--annotate", "--sign",
+        external=True,
+        # fmt: on
+    )
+    session.run("git", "push", "upstream", "master", release_version, external=True)