Drop Python 3.8/3.9 support, bump to version 5.0.0

[jensens]

Summary

Drop support for Python 3.8 and 3.9, bump to version 5.0.0 (major version), and modernize codebase to use Python 3.10+ features.

Breaking Changes

• Minimum Python version: 3.8 → 3.10
• Python 3.8 and 3.9 are no longer supported
• This is a major version bump (4.1.2 → 5.0.0) due to breaking backward compatibility

Changes

Configuration & Documentation (5 files)

1. pyproject.toml:

   • Updated requires-python = ">=3.10"
   • Removed Python 3.8/3.9 classifiers
   • Removed py38, py39 from tox env_list

2. Makefile:

   • Updated PYTHON_MIN_VERSION?=3.10

3. .github/workflows/tests.yaml:

   • Removed Python 3.8 and 3.9 from test matrix
   • CI now tests: Python 3.10, 3.11, 3.12, 3.13, 3.14 × 3 OS = 15 combinations (was 21)

4. CLAUDE.md:

   • Updated all Python version references from "3.8+" to "3.10+"
   • Updated documentation to reflect new minimum version

5. CHANGES.md:

   • Added version 5.0.0 section with breaking changes notice
   • Documented code modernization changes

Code Modernization (19 files)

Used ruff to automatically modernize type hints to Python 3.10+ syntax:

Type hint modernizations:

• typing.Dict[str, str] → dict[str, str]
• typing.List[str] → list[str]
• typing.Tuple[str, ...] → tuple[str, ...]
• typing.Set[str] → set[str]
• Optional[str] → str | None
• Union[str, int] → str | int
• Removed unused typing imports after conversion

String formatting modernizations:

• "text %s" % var → f"text {var}" (233 conversions)

Files affected:

• src/mxdev/*.py (5 files)
• src/mxdev/vcs/*.py (8 files)
• tests/*.py (6 files)

Testing

• ✅ All 174 tests pass locally on Python 3.14
• ✅ Code formatted and linted
• ✅ CI will test on Python 3.10-3.14 × 3 operating systems

Commits (6 total)

1. Update pyproject.toml: drop Python 3.8/3.9 support
2. Update Makefile: set minimum Python version to 3.10
3. Update CI workflow: remove Python 3.8/3.9 from test matrix
4. Update CLAUDE.md: Python 3.10+ minimum version
5. Bump version to 5.0.0 with breaking changes notice
6. Modernize type hints to Python 3.10+ syntax using ruff

Migration Guide for Users

Users running Python 3.8 or 3.9 should:

1. Upgrade to Python 3.10 or later
2. Pin to mxdev <5.0.0 if Python upgrade is not possible:

   mxdev<5.0.0
   

Rationale

• Python 3.8 EOL: October 2024 (already past)
• Python 3.9 EOL: October 2025 (approaching)
• Enables use of modern Python features (PEP 604 union syntax, built-in generic types)
• Reduces maintenance burden and testing matrix
• Aligns with modern Python ecosystem standards