extract-from-git.sh

#!/bin/bash
#Inspired by http://blog.neutrino.es/2012/git-copy-a-file-or-directory-from-another-repository-preserving-history/
#Hosted with revision at https://gist.github.com/nichtich/9196137

if test "$1" == ""; then
    echo "Usage $0 file-or-directory [directory-for-patches]"
    echo ""
    echo "Extract a file or directory from a git repository, preserving history. A"
    echo "temporary directory will be used if not directory for patches is provided."
    echo "The patches can be applied to a target repository with 'gim am *.patch'."
    exit 1
else
    PART=$1
fi

if test "$2" == ""; then
    DESTINATION=`mktemp -d`
else
    DESTINATION="$2"
fi

extract-from-git () {
    local part="$1"
    local destination="$2"
    git format-patch -o $destination --root HEAD -- $part
}

if test -f "$PART"; then
    extract-from-git "$PART" "$DESTINATION"
elif test -d "$PART"; then
    pushd $PART
    extract-from-git "$PART" "$DESTINATION"
    popd
else
    echo "$PART not found" 1>&2
    exit 1
fi

echo "# call 'git am $DESTINATION/*.patch' in your target repository to apply patches."