Created fail_if_not_git_repo function and prepended it to all git functions

lib/git/branch_shortcuts.sh

@@ -12,6 +12,7 @@
 # Adds numbered shortcuts to output of ls -l, just like 'git status'
 unalias $git_branch_alias > /dev/null 2>&1; unset -f $git_branch_alias > /dev/null 2>&1
 function _scmb_git_branch_shortcuts {
+  fail_if_not_git_repo || return 1
   # Fall back to normal git branch, if any unknown args given
   if [[ -n "$@" ]] && [[ "$@" != "-a" ]]; then
     $_git_cmd branch "$@"