misc: add pyupgrade files/notes (#55868)

.git-blame-ignore-revs

@@ -2,3 +2,5 @@
 47d67c395ef124ea4534ea7c56d48d4e302db430
 # misc: apply isort (#52797)
 29bc8e66a978b1bbadbc05186599a70ce1b8ef98
+# misc: apply pyupgrade (#55868)
+f4615c506194cf4eace0af551f14f54552f09dc5

.pre-commit-config.yaml

@@ -11,3 +11,8 @@ repos:
     hooks:
     - id: isort
       args: ['--profile', 'black', '--line-length', '110']
+-   repo: https://github.com/asottile/pyupgrade
+    rev: v2.20.0
+    hooks:
+    - id: pyupgrade
+      args: ['--keep-percent-format', '--py37-plus']

README

@@ -100,8 +100,13 @@ isort is used to format the imports, using those parameters:
 
     isort --profile black --line-length 110
 
-There is .pre-commit-config.yaml to use pre-commit to automatically run black and isort
-before commits. (execute `pre-commit install` to install the git hook.)
+pyupgrade is used to automatically upgrade syntax, using those parameters:
+
+    pyupgrade --keep-percent-format --py37-plus
+
+There is .pre-commit-config.yaml to use pre-commit to automatically run black,
+isort and pyupgrade before commits. (execute `pre-commit install` to install
+the git hook.)
 
 
 License