Fix non-existent / dangling refs cause Repository.prototype.createCommitWithSignature to fail#1624

implausible merged 5 commits into

nodegit:masternodegit/nodegit:masterfrom

emmax86:feature/sign-init-commit-on-bare-repoemmax86/nodegit:feature/sign-init-commit-on-bare-repoCopy head branch name to clipboard