GitHub Action: add support for the required-version "major-version-only" format when using pyproject.toml (#4770)

Co-authored-by: GiGaGon <107241144+MeGaGiGaGon@users.noreply.github.com>

Author: ericsampson

CHANGES.md

@@ -45,6 +45,9 @@
 
 <!-- For example, Docker, GitHub Actions, pre-commit, editors -->
 
+- Enhance GitHub Action `psf/black` to support the `required-version` major-version-only
+  "stability" format when using pyproject.toml (#4770)
+
 ### Documentation
 
 <!-- Major changes to documentation and policies. Small docs changes

action/main.py

@@ -68,7 +68,11 @@ def read_version_specifier_from_pyproject() -> str:
 
     version = pyproject.get("tool", {}).get("black", {}).get("required-version")
     if version is not None:
-        return f"=={version}"
+        # Match the two supported usages of `required-version`:
+        if "." in version:
+            return f"=={version}"
+        else:
+            return f"~={version}.0"
 
     arrays = [
         *pyproject.get("dependency-groups", {}).values(),