Defining custom sub commands, git example

git-sub-commands.sh

#!/bin/bash

## Custom git commands

unset -f git > /dev/null 2>&1 # Remove custom function if already set (i.e. if `reload` is called)
GIT=$(which git) # Get path to original git executable

git() {
  ERROR=1

  # Fail if not in a repository
  eval $GIT status > /dev/null
  if [ $? -ne 0 ]; then
    return $ERROR
  fi

  # Checkout a branch, applying the current changes
  if [ "$1" = "switch" ]; then
    if [ -z "$2" ]; then
      echo "Missing argument(s)" >&2
      echo "Usage: git switch <BRANCH_NAME>" >&2
      return $ERROR
    fi

    EXISTS=`eval $GIT rev-parse --quiet --verify $2`
    if [ -z "$EXISTS" ]; then
      echo "No branch named '$2'" >&2
      return $ERROR
    fi

    git stash 
    git checkout "$2"
    git stash apply

  # Hard reset to the origin of the current branch
  elif [ "$1" = "reset-origin" ]; then 
    CURRENT_BRANCH=`eval $GIT rev-parse --abbrev-ref HEAD`
    eval $GIT reset --hard origin/$CURRENT_BRANCH
  
  # If no matching custom command, execute against git
  else 
    eval $GIT "$@"
  fi
}