Add git.sh script

Allows for using git commands whilst specifying a SSH key to use.

See https://alvinabad.wordpress.com/2013/03/23/how-to-specify-an-ssh-key-file-with-the-git-command.

bin/git.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+ 
+# The MIT License (MIT)
+# Copyright (c) 2013 Alvin Abad
+ 
+if [ $# -eq 0 ]; then
+    echo "Git wrapper script that can specify an ssh-key file
+Usage:
+    git.sh -i ssh-key-file git-command
+    "
+    exit 1
+fi
+ 
+# remove temporary file on exit
+trap 'rm -f /tmp/.git_ssh.$$' 0
+ 
+if [ "$1" = "-i" ]; then
+    SSH_KEY=$2; shift; shift
+    echo "ssh -i $SSH_KEY \$@" > /tmp/.git_ssh.$$
+    chmod +x /tmp/.git_ssh.$$
+    export GIT_SSH=/tmp/.git_ssh.$$
+fi
+ 
+# in case the git command is repeated
+[ "$1" = "git" ] && shift
+ 
+# Run the git command
+git "$@"