Simple bash script to facilitate deploying projects to shared hosting using git

deploy.sh

#!/usr/bin/env bash

## This is a simple bash script to help deploy git-based projects to shared hostings.
## It work by tracking last deployed commit in a file (see below for file name).
## When you run this script, all files changed since last deployed commit up to now
## are put into a .tar.gz file (see below for file name), so you can easily upload and
## unzip it on shared hosting.

LAST_COMMIT_FILE=.last.deploy
OUTPUT_FILE=file.tar.gz

LAST_DEPLOYED_COMMIT=$(cat $LAST_COMMIT_FILE 2>/dev/null || git rev-list --max-parents=0 HEAD)
CURRENT_COMMIT=$(git rev-parse HEAD)

if [ "$LAST_DEPLOYED_COMMIT" = "$CURRENT_COMMIT" ]
then
    echo "Current commit already deployed"
    exit
fi

if [ -f $OUTPUT_FILE ]
then
    echo "Output file '$OUTPUT_FILE' already exists, please remove it first"
    exit
fi

git diff --name-only $LAST_DEPLOYED_COMMIT $CURRENT_COMMIT | tar -zcT - -f $OUTPUT_FILE

echo -n $CURRENT_COMMIT > $LAST_COMMIT_FILE