setup-git-demo

#!/usr/bin/env bash

set -euEo pipefail
trap 'echo "${BASH_SOURCE:-unknown}:${LINENO:-unknown}: $BASH_COMMAND";' ERR

# demo-start: go the beginning of the demo
git config --local alias.demo-start 'checkout --detach 0'

# demo-next: go to the next tag of the demo
git config --local alias.demo-next '!f() { git checkout --detach $((`git describe --tags` + 1)) && echo "git-demo: at step `git describe --tags`"; }; f'

# demo-prev: go to the previous tag of the demo
git config --local alias.demo-prev '!f() { git checkout --detach $((`git describe --tags` - 1)) && echo "git-demo: at step `git describe --tags`"; }; f'

# demo-tag: tag current commit
git config --local alias.demo-tag '!f() { last=$(git for-each-ref --sort="-version:refname" --count=1 --format="%(refname:short)" "refs/tags/*"); if [[ -z "${last}" ]]; then next=0; else next=$(($last + 1)); fi; git tag $next; }; f'