- * Find GIT_DIR of the repository that contains the current working directory,
- * without changing the working directory or other global state. The result is
- * appended to gitdir. The return value is either NULL if no repository was
- * found, or pointing to the path inside gitdir's buffer.
- */
-extern const char *discover_git_directory(struct strbuf *gitdir);
+ * Find the commondir and gitdir of the repository that contains the current
+ * working directory, without changing the working directory or other global
+ * state. The result is appended to commondir and gitdir. If the discovered
+ * gitdir does not correspond to a worktree, then 'commondir' and 'gitdir' will
+ * both have the same result appended to the buffer. The return value is
+ * either 0 upon success and non-zero if no repository was found.
+ */
+extern int discover_git_directory(struct strbuf *commondir,
+ struct strbuf *gitdir);