misc: add black files/notes

.git-blame-ignore-revs

@@ -0,0 +1,2 @@
+# trivial: apply black
+8089f03e4ab1432e705c2fba8706a0ea79dd8bbe

.pre-commit-config.yaml

@@ -0,0 +1,8 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+    - id: black
+      args: ['--target-version', 'py37', '--skip-string-normalization', '--line-length', '110']

README

@@ -23,6 +23,17 @@ CUT_GNM_OU_MAPPING
   }
 
 
+Code Style
+----------
+
+black is used to format the code, using thoses parameters:
+
+    black --target-version py37 --skip-string-normalization --line-length 110
+
+There is .pre-commit-config.yaml to use pre-commit to automatically run black
+before commits. (execute `pre-commit install` to install the git hook.)
+
+
 License
 -------