Add basic framework for pre-commit

This adds a standardized set of pre-commit checks which replicates
my (PWL) existing checks.

.pre-commit-config.yaml

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+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: local
+    hooks:
+    -  id: untracked-file
+       name: Untracked Files
+       language: system
+       entry: ./dev/untracked-files.sh
+       files: NONE
+       always_run: true
+       stages: [pre-commit, pre-push]
+    -  id: not-rfc
+       name: Not RFC
+       language: system
+       entry: ./dev/not-rfc.sh
+       files: NONE
+       always_run: true
+       stages: [pre-commit, pre-push]
+    -  id: run-tests
+       name: Running Test
+       language: system
+       entry: make pre-commit
+       files: NONE
+       always_run: true
+       stages: [pre-commit, pre-push]
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v3.2.0
+    hooks:
+    -   id: check-added-large-files
+

dev/not-rfc.sh

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+#!/bin/bash
+
+branch=$(git branch --show-current)
+if [ "$branch" = "rfc" ]; then
+    exit 0
+fi

dev/untracked-files.sh

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+#!/bin/bash
+set -eu
+
+files=$(git ls-files --other --directory --exclude-standard)
+if [ "$files" ]; then
+    echo There are untracked files: $files
+    exit 1
+fi