add feature to transparently fetch external potential files when a package is installed

# transparently fetch external files for a given package

fetch_potentials() {

    pdir="$1"

    shift

    type curl > /dev/null 2>&1 && have_curl=1 || have_curl=0

    type wget > /dev/null 2>&1 && have_wget=1 || have_wget=0

    if [ $have_curl -ne 1 ] && [ $have_wget -ne 1 ]

    then \

        echo "Need 'curl' or 'wget' to fetch external potential files"

        return

    fi

    while [ $# -gt 1 ]

    do \

        file=$1; sum=$2

        shift; shift

        echo ${sum} ${pdir}/${file} | md5sum -c - > /dev/null 2>&1 \

            && need_fetch=0 || need_fetch=1

        if [ ${need_fetch} -eq 1 ]

        then \

            url="https://download.lammps.org/potentials/${file}.${sum}"

            echo "Fetching external potential file ${file} from ${url}"

            if [ ${have_curl} ]

            then \

                curl -L -o ${pdir}/${file} ${url}

            elif [ ${have_wget} ]

            then \

                wget -O ${pdir}/${file} ${url}

            fi

        fi

   done

}

if [ -f "$1/potentials.txt" ]

then

    fetch_potentials "$1/../../potentials" `sed -e 's/#.*$//' "$1/potentials.txt"`

fi

tar:

	@cd STUBS; $(MAKE) clean

	@cd ..; tar cvzf src/$(ROOT)_src.tar.gz \

	  src/Make* src/Package.sh src/Depend.sh src/Install.sh \

	  src/Make* src/Package.sh src/Depend.sh src/Install.sh src/Fetch.sh \

	  src/MAKE src/DEPEND src/*.cpp src/*.h src/STUBS \

	  $(patsubst %,src/%,$(PACKAGEUC)) $(patsubst %,src/%,$(PACKUSERUC)) \

          --exclude=*/.svn

	  cd $(YESDIR); $(SHELL) ../Install.sh 1; cd ..; \

		$(SHELL) Depend.sh $(YESDIR) 1; \

	fi;

	@$(SHELL) Fetch.sh $(YESDIR)

no-%:

	@if [ ! -e $(NODIR) ]; then \

# list of potential files to be fetched when this package is installed

# potential file  md5sum

C_10_10.mesocnt 028de73ec828b7830d762702eda571c1