[BUG] Regression: Compilation fails with git worktree

Created by: bodograumann

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
What's the version of OpenAPI Generator used?
Have you search for related issues/PRs?
What's the actual output vs expected output?

Description

When checking out the openapi-generator code in a git worktree, compilation will not work.

openapi-generator version

master

Bug was introduced in e14e5fcc due to the inclusion of git-commit-id-plugin.

Steps to reproduce

git clone https://github.com/openapitools/openapi-generator
cd openapi-generator
git worktree add ../openapi-generator-dev
cd ../openapi-generator-dev
mvn clean package

This will throw an error:

[ERROR] Failed to execute goal pl.project13.maven:git-commit-id-plugin:4.0.0:revision (get-the-git-infos) on project openapi-generator: Could not complete Mojo execution...: Error: Could not get HEAD Ref, are you sure you have some commits in the dotGitDirectory? -> [Help 1]

Related issues/PRs

This is caused by missing git worktree support in git-commit-id-maven-plugin. That in turn is caused by the feature missing in JGit

Suggest a fix

A possible approach would be to disable the plugin -Dmaven.gitcommitid.skip=true during compilation. This will make openapi-generator (core library) compile successfully, but cause test errors in openapi-generator (executable) unfortunately.

Not sure how a proper fix would look like. At least this behaviour should be documented somewhere.