+ * ".git" followed by NUL or slash is bad. Note that we match
+ * case-insensitively here, even if ignore_case is not set.
+ * This outlaws ".GIT" everywhere out of an abundance of caution,
+ * since there's really no good reason to allow it.
+ *
+ * Once we've seen ".git", we can also find ".gitmodules", etc (also
+ * case-insensitively).