Extension property for Gradle's Project interface to figure out the Git root, if any

findProjectGitRoot.kt

package dev.sebastiano.utils.gradle

import org.gradle.api.*
import java.io.*

// Note: you need to have a dependency on `gradleApi()` in your buildSrc project

val Project.gitRoot: File?
    get() {
        fun File.isGitRoot() = isDirectory && File(this, ".git").isDirectory
        fun File.findGitRoot(): File? = if (isGitRoot()) {
            this
        } else parentFile?.findGitRoot()

        return rootDir.findGitRoot()
    }
    

Note that this snippet will traverse the filesystem up to the volume root, and report the first Git root it finds. It has no way to verify it's the correct one.