The success of an open-source project depends to a large degree on the proactive and constructive participation by the developer community. An important role that developers play in a project is that of a code committer. However, code-commit privilege is typically restricted to the core group of a project. In this paper, we study the phenomenon of the induction of external developers as code committers. The trustworthiness of an external developer is one of the key factors that determines the granting of commit privileges. Therefore, we formulate different hypotheses to explain how the trust is established in practice. To investigate our hypotheses, we developed an automated approach based on mining code repositories and bug-tracking systems. We implemented the approach and performed an empirical study, using the Eclipse projects, to test the hypotheses. Our results indicate that, most frequently, developers establish trust and credibility in a project by contributing to the project in a non-committer role. Moreover, the employing organization of a developer is another factor--although a less significant one--that influences trust.