Revert "Temporarily remove pip.yml, to avoid GHA failures while waiting for a fix on master."

This reverts commit 3cef809281.

.github/workflows/pip.yml

@@ -0,0 +1,111 @@
+name: Pip
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+    - master
+    - stable
+    - smart_holder
+    - v*
+  release:
+    types:
+    - published
+
+env:
+  PIP_ONLY_BINARY: numpy
+
+jobs:
+  # This builds the sdists and wheels and makes sure the files are exactly as
+  # expected. Using Windows and Python 3.6, since that is often the most
+  # challenging matrix element.
+  test-packaging:
+    name: 🐍 3.6 • 📦 tests • windows-latest
+    runs-on: windows-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Setup 🐍 3.6
+      uses: actions/setup-python@v4
+      with:
+        python-version: 3.6
+
+    - name: Prepare env
+      run: |
+        python -m pip install -r tests/requirements.txt
+
+    - name: Python Packaging tests
+      run: pytest tests/extra_python_package/
+
+
+  # This runs the packaging tests and also builds and saves the packages as
+  # artifacts.
+  packaging:
+    name: 🐍 3.8 • 📦 & 📦 tests • ubuntu-latest
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Setup 🐍 3.8
+      uses: actions/setup-python@v4
+      with:
+        python-version: 3.8
+
+    - name: Prepare env
+      run: |
+        python -m pip install -r tests/requirements.txt build twine
+
+    - name: Python Packaging tests
+      run: pytest tests/extra_python_package/
+
+    - name: Build SDist and wheels
+      run: |
+        python -m build
+        PYBIND11_GLOBAL_SDIST=1 python -m build
+
+    - name: Check metadata
+      run: twine check dist/*
+
+    - name: Save standard package
+      uses: actions/upload-artifact@v3
+      with:
+        name: standard
+        path: dist/pybind11-*
+
+    - name: Save global package
+      uses: actions/upload-artifact@v3
+      with:
+        name: global
+        path: dist/pybind11_global-*
+
+
+
+  # When a GitHub release is made, upload the artifacts to PyPI
+  upload:
+    name: Upload to PyPI
+    runs-on: ubuntu-latest
+    if: github.event_name == 'release' && github.event.action == 'published'
+    needs: [packaging]
+
+    steps:
+    - uses: actions/setup-python@v4
+      with:
+        python-version: "3.x"
+
+    # Downloads all to directories matching the artifact names
+    - uses: actions/download-artifact@v3
+
+    - name: Publish standard package
+      uses: pypa/gh-action-pypi-publish@v1.6.4
+      with:
+        password: ${{ secrets.pypi_password }}
+        packages_dir: standard/
+
+    - name: Publish global package
+      uses: pypa/gh-action-pypi-publish@v1.6.4
+      with:
+        password: ${{ secrets.pypi_password_global }}
+        packages_dir: global/