Add reusable lint workflow

.flake8

@@ -0,0 +1,7 @@
+[flake8]
+# Based directly on Black's recommendations:
+# https://black.readthedocs.io/en/stable/the_black_code_style.html#line-length
+max-line-length = 81
+select = A,C,E,F,W,B,B950
+#B305 doesn't like `.next()` that is a key Tree method.
+ignore = E203, E501, W503, B305

.github/workflows/tests.yml

@@ -3,10 +3,13 @@ name: Tests
 on:
   pull_request:
   push:
-    branches: [main]
+    branches: [main, test]
   merge_group:
 
 jobs:
+  pre-commit:
+    name: Lint
+    uses: tskit-dev/.github/.github/workflows/lint.yml@v1
   test:
     name: Python
     runs-on: ${{ matrix.os }}

.pre-commit-config.yaml

@@ -0,0 +1,36 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v6.0.0
+    hooks:
+      - id: check-merge-conflict
+      - id: debug-statements
+      - id: mixed-line-ending
+      - id: check-case-conflict
+      - id: check-yaml
+  - repo: https://github.com/asottile/reorder_python_imports
+    rev: v3.15.0
+    hooks:
+      - id: reorder-python-imports
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v3.20.0
+    hooks:
+      - id: pyupgrade
+        args: [--py3-plus, --py38-plus]
+  - repo: https://github.com/psf/black
+    rev: 25.1.0
+    hooks:
+      - id: black
+        language_version: python3
+  - repo: https://github.com/pycqa/flake8
+    rev: 7.3.0
+    hooks:
+      - id: flake8
+        args: [--config=.flake8]
+        additional_dependencies: ["flake8-bugbear==23.9.16", "flake8-builtins==2.1.0"]
+  - repo: https://github.com/asottile/blacken-docs
+    rev: 1.20.0
+    hooks:
+      - id: blacken-docs
+        args: [--skip-errors]
+        additional_dependencies: [black==22.3.0]
+        language_version: python3