Fix & improve github.createTag

[MattSturgeon]

Fixed the inverted logic and avoided the need to fetch all repo tags by using getRef instead.

I tested out the hasRef implementation as follows:

Details

// Some boilerplate setting up github, token & repo omitted
fun main() {
    sequenceOf("v1.2.3", "foo", "random", "v1.2.2", "v1.2.3+mc1.20.4")
        .forEach {
            println("Checking if ${repo.fullName} has tag named $it")
            val has = repo.hasTag(it)
            println("  It ${if (has) "does" else "does not"}!")
        }

}

fun GHRepository.hasTag(tag: String): Boolean {
    try {
        this.getRef("refs/tags/$tag")
        return true
    } catch (e: GHFileNotFoundException) {
        return false
    } catch (e: IOException) {
        throw IOException("Error checking remote tag", e)
    }
}

Which prints:

Checking if MinecraftFreecam/Freecam has tag named v1.2.3
  It does!
Checking if MinecraftFreecam/Freecam has tag named foo
  It does not!
Checking if MinecraftFreecam/Freecam has tag named random
  It does not!
Checking if MinecraftFreecam/Freecam has tag named v1.2.2
  It does!
Checking if MinecraftFreecam/Freecam has tag named v1.2.3+mc1.20.4
  It does!

Fixes #12
Fixes #14

[MattSturgeon]

This API was broken and is marked "experimental". Should we take this opportunity to change behaviour for the creating a draft scenario?

What do you think the best approach is?

• rename the option for clarity?
• just update the docs?
• add draft/public specific options?
• take a string/enum instead of a boolean?

[hypherionmc]

Hey. Just checking in. I've been so busy I forgot to check back on things.

Is this PR ready to be merged, or do you have more you want to do first?

[MattSturgeon]

I've been so busy I forgot to check back on things.

No worries 👍

Is this PR ready to be merged

Should be good to go, unless you request any changes.

do you have more you want to do first?

It doesn't address this comment or any of the ideas discussed in #16, but it does fix actual issues in the current implementation.

Those other changes are out of scope of this PR, I think.