Better Javadoc.

core/src/main/java/hudson/scm/SCM.java

@@ -700,7 +700,10 @@ public abstract class SCM implements Describable<SCM>, ExtensionPoint {
     }
 
     /**
-     * Returns the list of {@link SCMDescriptor}s that are applicable to the given project.
+     * Determines which kinds of SCMs are applicable to a given project.
+     * @param project a project on which we might be configuring SCM, or null if unknown
+     * @return all descriptors which {@link SCMDescriptor#isApplicable(Job)} to it, also filtered by {@link TopLevelItemDescriptor#isApplicable};
+     *         or simply {@link #all} if there is no project
      * @since 1.568
      */
     public static List<SCMDescriptor<?>> _for(@CheckForNull final Job project) {