ctags

#! /bin/sh

GITDIR=$(git rev-parse --git-dir)
TAGSFILE=tags.$$

mkdir $GITDIR/tags_lock 2>/dev/null || exit 0
trap "rmdir $GITDIR/tags_lock; rm $GITDIR/$TAGSFILE" EXIT

# normal ctags
ctags --tag-relative -Rf $GITDIR/$TAGSFILE --exclude=$GITDIR

# haskell ctags
if which hasktags > /dev/null ; then
    OLD_DIR=$(pwd)
    (cd $GITDIR && hasktags -c -x --ignore-close-implementation -a -f $TAGSFILE $OLD_DIR)
    LC_COLLATE=C sort $GITDIR/$TAGSFILE -o $GITDIR/$TAGSFILE
fi

mv $GITDIR/$TAGSFILE $GITDIR/tags

Use with http://tbaggery.com/2011/08/08/effortless-ctags-with-git.html#comment-728214764.