pre-commit hook (add to .git/hooks/pre-commit) to refuse to commit debugger strings. Note list of file extensions to see which files are conisdered.

pre-commit.sh

#!/bin/sh
# Refuse to commit files with the string NOCOMMIT, debugger, or merge markers present.
#

files=$(git diff-index --name-status --cached HEAD | grep -v ^D | cut -c3-)

if [ "$files" != "" ]
then
  for f in $files
  do
    if [[ "$f" =~ [.](ts|java|conf|css|html|js|json|log|properties|txt|xml|yml)$ ]]
    then
      if [ "$(grep NOCOMMIT $f)" != '' ]
      then
        echo "NOCOMMIT message present in file $f, aborting!"
        echo "$(grep -n -C 3 NOCOMMIT $f)"
        exit 1
      fi
      if [ "$(grep debugger $f)" != '' ]
      then
        echo "debugger present in file $f, aborting!"
        echo "$(grep -n -C 3 debugger $f)"
        exit 1
      fi
      if [ "$(grep '<<<<<<<' $f)" != '' ]
      then
        echo "merge markers present in file $f, aborting!"
        echo "$(grep -n -C 3 '<<<<<<<' $f)"
        exit 1
      fi
    fi
  done
fi