This script helps in creating a tar.gz file containing only modified and added files from between two commits in a git repository. The idea is for deployed applications, to update only the changed files for a hotfix or small update, this tar can be created and extracted over that existing directory. Of course this only works if there were additi…

createPatchTarBetween.sh

#/bin/bash -e

START_BRANCH="$1"
END_BRANCH="$2"
PATCH_TAR=patch.tar.gz
COMMIT_HASH_FILE=commit_hash

usage(){
    echo ""
    echo "USAGE: $0 START END"
    echo ""
    echo "   START and END mark the beginning and end commits that define the patch. The"
    echo "   arguments can be branch names, tag names, or commit hashes. The script file"
    echo "   must be invoked from within the top level of the repository. The script    "
    echo "   file itself can live anywhere.                                             "
    echo "" 
    echo "   Creating a patch tar only works if no files were deleted or renamed. Only  "
    echo "   modifications and additions make sense. The reason is this tar will be     "
    echo "   extracted over the existing directory, replacing modified files and adding "
    echo "   any new files. Files cannot be deleted from the existing directory by      "
    echo "   extracting a tar file over it. If any deletions or renames are detected, a "
    echo "   WARNING message will be displayed as well as some warnings from the tar    "
    echo "   create command.                                                            "
    echo ""
}

checkArguments(){
    if [ $# -ne 2 ]; then
        usage
        exit 1
    fi
}

warnOfDeletes(){
    local warning="WARNING: Differences contain deletes or renames. Patching won't work by simply untaring patch"
    diffOutput | awk '{print $1}' | egrep "[CDRTUXB]" > /dev/null && echo "${warning}" >&2
}

createCommitHash(){
    git show -s --format=%H HEAD > "${COMMIT_HASH_FILE}"
}

createPatch(){
    diffOutput | awk "{print \$2} END {print \"${COMMIT_HASH_FILE}\"}" | tar czf "${PATCH_TAR}" -T -
    echo "Created '${PATCH_TAR}'"
}

diffOutput(){
    git diff --name-status "${START_BRANCH}" "${END_BRANCH}" | awk '{if ($2 !~ /(spec\/|features\/)/) {print $0}}'
}

cleanup(){
    rm "${COMMIT_HASH_FILE}"
}

checkArguments "$@"
warnOfDeletes
createCommitHash
createPatch
cleanup