git wrapper for JASMIN sci machines

Git

#!/bin/bash
#============================
#  A wrapper for git, for use on JASMIN.  In most cases, it will just invoke
#  git with the supplied command line arguments, but if you are on a physical
#  sci machine and you are trying to talk to a non-http (i.e. ssh) repo URL,
#  then it uses ssh to a sci VM in order to run the same command.  This is
#  because the networking arrangements don't permit this from the sci-ph
#  machines.
#============================

script_args=("$@")

needs_remote() {
    case ${script_args[0]} in
	fetch|pull|push|clone) return 0;;
	*) return 1;;
    esac
}

is_172_private_network() {
    gateway=$(ip route show default | awk '{print $3}')
    [[ "$gateway" =~ ^172\.(1[6-9]|2[0-9]|3[0-1])\. ]]
}

is_http_url() {
    if [ ${script_args[0]} = clone ]
    then
	url=${script_args[1]}
    else
	# LIMITATION: assumes that the remote is origin
	# could be improved so that it parses the command args
	url=$(git remote get-url origin)
    fi
    [[ "$url" =~ ^http ]]  # includes https
}

get_sci_vm() {
    # get hostname of a sci VM that is responding to ping
    for host in sci-vm-0{1..5}
    do
	if ping -c1 -w1 $host > /dev/null
	then
	    echo $host
	    return
	fi
    done
    echo "no sci vm available" >& 2
    exit 1
}

local_dir() {
    case $(pwd) in
	/tmp*|/var/tmp*) return 0;;
	*) return 1;;
    esac
}

if ! needs_remote || ! is_172_private_network || is_http_url
then
     git "$script_args"
elif local_dir
then
     echo "this might hang - consider using https URL" >&2
     git "$script_args"
else
    vm=$(get_sci_vm)
    echo "using $vm" >&2
    dir=$(pwd)
    ssh -Ax $vm "cd $dir && git $@"
fi