pre-commit

#!/bin/sh
#
# An example hook script to verify what is about to be committed.
# Called by "git commit" with no arguments.  The hook should
# exit with non-zero status after issuing an appropriate message if
# it wants to stop the commit.
#
# To enable this hook, rename this file to "pre-commit".

against=$(git rev-parse --verify HEAD 2>/dev/null || echo 4b825dc642cb6eb9a060e54bf8d69288fbee4904)
# 4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the hash of the empty tree, used if there is no HEAD yet (initial commit)

# If you want to allow non-ascii filenames set this variable to true.
allownonascii=$(git config hooks.allownonascii)

# Cross platform projects tend to avoid non-ascii filenames; prevent
# them from being added to the repository. We exploit the fact that the
# printable range starts at the space character and ends with tilde.
if [ "$allownonascii" != "true" ] &&
        # Note that the use of brackets around a tr range is ok here, (it's
        # even required, for portability to Solaris 10's /usr/bin/tr), since
        # the square bracket bytes happen to fall in the designated range.
        test "$(git diff --cached --name-only --diff-filter=A -z $against |
          LC_ALL=C tr -d '[ -~]\0')"
then
        cat 1>&2 << EOF
Error: Attempt to add a non-ascii file name.

This can cause problems if you want to work
with people on other platforms.

To be portable it is advisable to rename the file ...

If you know what you are doing you can disable this
check using:

    git config hooks.allownonascii true

EOF
        exit 1
fi

# If you want to allow filename that differ only by case set this variable to true.
allowcasecollision=$(git config hooks.allowcasecollision)

if [ "$allowcasecollision" != "true" ] &&
        test "$(git diff --cached --name-only --diff-filter=A | 
          LC_ALL=C tr [A-Z] [a-z] | 
          sort | 
          uniq --repeated )"
then
        cat 1>&2 << EOF
Error: Attempt to add a file name which differs only by case from
another tracked file.

This can cause problems if you want to work
with people on other platforms.

To be portable it is advisable to rename the file ...

If you know what you are doing you can disable this
check using:

    git config hooks.allowcasecollision true

EOF
        exit 1
fi

exec git diff-index --check --cached $against --