Little shell script for automating switching between different Git tags in a presentation.

tags.sh

#!/usr/bin/env bash

set -e

CACHE_FILE="$HOME/.tags-cache"

if [ -f "$CACHE_FILE" ]; then
    CURRENT_TAG=$(<"$CACHE_FILE")
else
    unset CURRENT_TAG
fi

if [ -z ${TAG_PREFIX+x} ]; then
    TAG_PREFIX=""
fi

function checktag() {
    if [ -z ${CURRENT_TAG+x} ]; then
        echo "No tag currently set. Use 'jump'."
        exit 1
    fi
}

function jumptag() {
    git reset --hard
    git checkout "$TAG_PREFIX$CURRENT_TAG"
    git reset --soft HEAD^
}

function savetag() {
    touch "$CACHE_FILE"
    echo "$CURRENT_TAG" > "$CACHE_FILE"
}

case "$1" in
    next | n)
        checktag
        let CURRENT_TAG+=1
        jumptag
        savetag
        ;;
    prev | p)
        checktag
        let CURRENT_TAG+=-1
        jumptag
        savetag
        ;;
    jump | j)
        CURRENT_TAG="$2"
        jumptag
        savetag
        ;;
    kill | k)
        rm "$CACHE_FILE"
        ;;
    *)
        echo "Usage: ./tags.sh CMD [DEST]"
        echo "where CMD can be one of"
        echo "  next"
        echo "  prev"
        echo "  jump DEST"
        echo "  kill"
        echo "and DEST is a tag number."
        ;;
esac