src/third_party/chromium/src/build/git-hooks/pre-commit

#!/bin/sh

submods=$(git diff-index --cached --ignore-submodules=dirty HEAD | grep -e '^:160000' -e '^:...... 160000' | xargs)
if test "$submods"; then
  echo "You are trying to commit changes to the following submodules:" 1>&2
  echo 1>&2
  echo $submods | cut -d ' ' -f 6 | sed 's/^/  /g' 1>&2
  cat <<EOF 1>&2

Submodule commits are not allowed.  Please run:

  git status --ignore-submodules=dirty

and/or:

  git diff-index --cached --ignore-submodules=dirty HEAD

... to see what's in your index.

If you're really and truly trying to roll the version of a submodule, you should
commit the new version to DEPS, instead.
EOF
  exit 1
fi

if test "$(git diff-index --cached HEAD .gitmodules)"; then
  cat <<EOF 1>&2
You are trying to commit a change to .gitmodules.  That is not allowed.
To make changes to submodule names/paths, edit DEPS.
EOF
  exit 1
fi

exit 0