in nb-shared/src/main/java/org/apache/netbeans/nbm/utils/ExamineManifest.java [309:320]
public void setArtifactFile(File artifactFileLoc) {
if (artifactFileLoc.isFile()) {
setJarFile(artifactFileLoc);
} else if (artifactFileLoc.isDirectory()) {
File mani = new File(artifactFileLoc, "META-INF/MANIFEST.MF");
if (mani.isFile()) {
setManifestFile(mani);
} // else e.g. jarprj/target/classes has no manifest, so nothing to examine
} else {
throw new IllegalArgumentException(artifactFileLoc.getAbsolutePath());
}
}