Do not create tag if it was created on same commit as current branch

[pionl]

Hi, thanks for the great script! Before I've checked the issue I wanted this feature too.

I've tried on clean repo, made changes, etc..

Resolves #3

[MichaelCurrin]

thanks for the contribution! I'll test it out

[MichaelCurrin]

It's more elegant to use the not empty check than to check if filled and negate

https://devhints.io/bash

Suggested change

	if [[ ! -z "$LAST_TAG" ]]; then
	if [[ -n "$LAST_TAG" ]]; then

[MichaelCurrin]

Rather make it an error.

Suggested change

	exit 0;
	exit 1

[MichaelCurrin]

If you use rev-parse it already gets one commit so you don't have to set it.

https://michaelcurrin.github.io/dev-cheatsheets/cheatsheets/version-control/git/advanced.html

And if you use HEAD, that already points to the current commit. No branch name needed.

Suggested change

	BRANCH_HASH=$(git rev-list -n 1 $CURRENT_BRANCH)
	BRANCH_HASH=$(git rev-parse HEAD)

[MichaelCurrin]

Suggested change

	LAST_TAG_HASH=$(git rev-list -n 1 $LAST_TAG)
	LAST_TAG_HASH=$(git rev-parse $LAST_TAG)

[MichaelCurrin]

No longer needed. See below.

Suggested change

CURRENT_BRANCH=$(git branch --show-current)

[MichaelCurrin]

I've used double equals elsewhere in the script, so remain consistent with that. Same behavior though.

Suggested change

	if [[ "$BRANCH_HASH" = "$LAST_TAG_HASH" ]]; then
	if [[ "$BRANCH_HASH" == "$LAST_TAG_HASH" ]]; then

[MichaelCurrin]

Suggested change

	# Ensure that tag is not created on same commit as current branch commit
	# Check if the current commit is already tagged.

[MichaelCurrin]

That's quiet a mouthful. Just say the thing that we are watching out for and alert on it.

Suggested change

	echo "Last tag is on the same commit as current branch";
	echo "The current commit already has a commit on it. Aborting, to avoid tagging it again."

Trailing semi-colons are superfluous here. Got JavaScript / Java on the brain?

[MichaelCurrin]

I made some refactor suggestions, so that you can learn more about the shell and git.

But closing this PR because of alternative covered below.

[MichaelCurrin]

A more elegant solution is to use git's built-in check for whether a commit is tagged or not.

Try this out in your terminal.

git describe --tags --exact-match HEAD &> /dev/null \
  && echo 'Commit is tagged' \
  || echo 'Commit is NOT tagged'

Thanks to --exact-match flag - if the commit reference is tagged, you'll get details as usual. But if no tag is found, then it will give an error status.

And then that can be adapted. I've made PR #11 as a shorter form and replacement of what you are doing here. I'd appreciate your review of that please.