ci: create GitHub Action that squashes all typo PRs into a single PR (#15041)

The action adds all pull-request authors (and Marvim) as a co-author to the
newly created PR and also links to the closed PRs.

.github/workflows/squash-typos.yml

@@ -0,0 +1,32 @@
+name: Squash Typo Pull Requests
+
+on:
+  pull_request:
+    types: labeled
+concurrency:
+  group: ${{ github.workflow }} 
+jobs:
+  build:
+    if: github.event.label.name == 'typo'
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: write
+      pull-requests: write
+
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+        ref: master
+    - uses: actions/setup-python@v2
+
+    - name: Setup git config
+      run: |
+        git config --global user.name 'marvim'
+        git config --global user.email 'marvim@users.noreply.github.com'
+
+    - run: python scripts/squash_typos.py

scripts/squash_typos.py

@@ -0,0 +1,148 @@
+#!/usr/bin/env python
+"""
+
+This script squashes a PR tagged with the "typo" label into a single, dedicated
+"squash PR".
+
+"""
+
+import subprocess
+import os
+import re
+
+
+def get_authors_and_emails_from_pr():
+    """
+
+    For a given PR number, returns all contributing authors and their emails
+    for that PR. This includes co-authors, meaning that if two authors are
+    credited for a single commit, which is possible with GitHub, then both will
+    get credited.
+
+    """
+
+    # Get a list of all authors involved in the pull request (including co-authors).
+    authors = subprocess.check_output(
+        ["gh", "pr", "view", "--json", "commits", "--jq", ".[][].authors.[].name"],
+        text=True,
+    ).splitlines()
+
+    # Get a list of emails of the aforementioned authors.
+    emails = subprocess.check_output(
+        ["gh", "pr", "view", "--json", "commits", "--jq", ".[][].authors.[].email"],
+        text=True,
+    ).splitlines()
+
+    return [(author, mail) for author, mail in zip(authors, emails)]
+
+
+def rebase_onto_pr(pr, squash_branch):
+    """
+
+    Add all commits from PR into current branch. This is done by rebasing
+    current branch onto the PR.
+
+    """
+
+    # Check out the pull request.
+    subprocess.call(["gh", "pr", "checkout", pr])
+
+    pr_branch_name = subprocess.check_output(
+        ["git", "branch", "--show-current"], text=True
+    ).strip()
+
+    # Change back to the original branch.
+    subprocess.call(["git", "switch", squash_branch])
+
+    # Rebase onto the pull request, aka include the commits in the pull
+    # request in the current branch.
+    subprocess.call(["git", "rebase", pr_branch_name])
+
+
+def squash_all_commits():
+    """
+
+    Squash all commits into a single commit. Credit all authors by name and
+    email.
+
+    """
+
+    authors_and_emails = get_authors_and_emails_from_pr()
+    subprocess.call(["git", "reset", "--soft", f"{os.environ['GITHUB_BASE_REF']}"])
+
+    authors_and_emails = sorted(set(authors_and_emails))
+    commit_message_coauthors = "\n" + "\n".join(
+        [f"Co-authored-by: {i[0]} <{i[1]}>" for i in authors_and_emails]
+    )
+    subprocess.call(
+        ["git", "commit", "-m", "chore: typo fixes", "-m", commit_message_coauthors]
+    )
+
+
+def force_push(branch):
+    gh_actor = os.environ["GITHUB_ACTOR"]
+    gh_token = os.environ["GITHUB_TOKEN"]
+    gh_repo = os.environ["GITHUB_REPOSITORY"]
+    subprocess.call(
+        [
+            "git",
+            "push",
+            "--force",
+            f"https://{gh_actor}:{gh_token}@github.com/{gh_repo}",
+            branch,
+        ]
+    )
+
+
+def main():
+    squash_branch = "marvim/squash-typos"
+    all_pr_urls = ""
+
+    pr_number = re.sub(r"\D", "", os.environ["GITHUB_REF"])
+
+    show_ref_output = subprocess.check_output(["git", "show-ref"], text=True).strip()
+
+    if squash_branch in show_ref_output:
+        subprocess.call(
+            ["git", "checkout", "-b", squash_branch, f"origin/{squash_branch}"]
+        )
+        squash_branch_exists = True
+
+        all_pr_urls += subprocess.check_output(
+            ["gh", "pr", "view", "--json", "body", "--jq", ".body"], text=True
+        )
+    else:
+        subprocess.call(["git", "checkout", "-b", squash_branch])
+        squash_branch_exists = False
+
+    all_pr_urls += subprocess.check_output(
+        ["gh", "pr", "view", pr_number, "--json", "url", "--jq", ".url"], text=True
+    ).strip()
+
+    rebase_onto_pr(pr_number, squash_branch)
+    force_push(squash_branch)
+
+    subprocess.call(["gh", "pr", "close", pr_number])
+
+    squash_all_commits()
+    force_push(squash_branch)
+
+    if not squash_branch_exists:
+        subprocess.call(
+            [
+                "gh",
+                "pr",
+                "create",
+                "--fill",
+                "--head",
+                squash_branch,
+                "--title",
+                "Dedicated PR for all typo fixes.",
+            ]
+        )
+
+    subprocess.call(["gh", "pr", "edit", "--add-label", "typo", "--body", all_pr_urls])
+
+
+if __name__ == "__main__":
+    main()