scripts: add todo_diff.sh

Adds a shell script to find `TODO`s that have been added between two commits.

Relates to #62552.

Release note: None

scripts/todo_diff.sh

@@ -0,0 +1,78 @@
+#!/bin/bash
+
+# The command runs git diff between two refspecs to find all instances of TODO
+# added between them.
+
+cmd=$(basename "$0")
+__usage="${cmd} finds TODOs in pkg added in a release branch since a release tag.
+It prints the results to stdout. The optional third argument represents the
+directory within the repo to search.
+
+Usage: ${cmd} <release-tag> <release-branch> [<diff-path>]"
+
+set -euo pipefail
+
+SEARCH_DIR="pkg"
+
+case $# in
+  2) ;;
+  3) SEARCH_DIR="$3" ;;
+  *)
+    echo >&2 "${__usage}"
+    exit 1
+    ;;
+esac
+
+ORIGINAL_BRANCH=$(git branch --show-current)
+TAG=$1
+BRANCH=$2
+UPSTREAM=$(git remote -v | grep 'cockroachdb/cockroach' | { read -r UPSTREAM rest; echo "${UPSTREAM}"; } )
+
+setup() {
+
+  # Pull latest upstream.
+  git fetch --quiet "${UPSTREAM}"
+
+  # Checkout the old release tag.
+  git checkout --quiet "tags/${TAG}"
+
+  # Checkout the new files for the search directory.
+  git checkout --quiet "${UPSTREAM}/${BRANCH}" "${SEARCH_DIR}"
+
+  # Reset.
+  git reset --quiet HEAD "${SEARCH_DIR}"
+
+  # Add all untracked files to the index so they will show results with git diff.
+  git add -AN "${SEARCH_DIR}"
+}
+
+cleanup() {
+  git restore --quiet --staged "${SEARCH_DIR}"
+  git restore --quiet "${SEARCH_DIR}"
+  git clean --quiet -f "${SEARCH_DIR}"
+  git checkout --quiet --no-recurse-submodules "${ORIGINAL_BRANCH}"
+}
+
+diff_file() {
+    __file="$1"
+    git diff -G'TODO' "${__file}" \
+      | {
+      # Use a subshell because grep returns a non-zero exit code with no matches.
+      # The pattern will match a leading + and then anything such that there is
+      # a subsequent TODO and the character preceding it is either a whitespace,
+      # #, or /.
+      grep -E '^\+(.*[[:space:]#/])?TODO' || true
+    } \
+      | sed 's|^\+[[:space:]]*\(.*\)|'"${__file}"': \1|g'
+}
+
+run() {
+  while read -r -s p || [[ -n "${p}" ]]
+  do
+    diff_file "${p}"
+  done < <( git diff -G'TODO' --name-only "${SEARCH_DIR}" )
+}
+
+trap cleanup >&2 EXIT
+setup >&2
+run