Add tag

[minhluong96]

Add git describe --tag into result

[nexdrew]

@minhluong96 Thanks for the contribution! 😺 I like this idea, but I have a couple concerns:

1. Does it make sense to always provide results of both git rev-parse HEAD and git describe --tags, or should the consumer specify which one they want (and then it just gets returned as the id result)? I can imagine an option like a boolean useTag or maybe even a string (or array of strings) that specifies the git command to use.

2. If we do always just return both, then it seems like (a) we could possibly run both git commands concurrently via Promise.all() and (b) we could easily refactor the code to reduce duplicate logic between the determineBuildTag and determineBuildId functions.

3. We need to fix broken tests, add new assertions for the result of the tag prop, and add a new test for when tag is predefined in opts.

Let me know what you think.