Use current git repository as the default for github-pages plugin

[mojavelinux]

Right now, it's necessary to specify the repoUri explicitly. In most cases, however, the git repository for GitHub Pages is the same as the repository for the project. Therefore, it would be very convenient if the repoUri was set to the git property remote.origin.url by default.

Since there's currently no default, this change shouldn't break any existing users.

The behavior I'm describing is how the gh-pages npm package, commonly used in Gulp builds. (See https://www.npmjs.com/package/gh-pages#optionsrepo).

In the meantime, I found a workaround using JGit directly. But it's not very elegant.

repoUri = new org.eclipse.jgit.lib.RepositoryBuilder()
      .readEnvironment().findGitDir(file('.')).build()
      .getConfig().getString('remote', 'origin', 'url')

[ajoberstar]

Also makes sense.

[mojavelinux]

👍