[FIXED JENKINS-19473] Trying to work around jzlib bug.

changelog.html

@@ -55,7 +55,9 @@ Upcoming changes</a>
 <!-- Record your changes in the trunk here. -->
 <div id="trunk" style="display:none"><!--=TRUNK-BEGIN=-->
 <ul class=image>
-  <li class=>
+  <li class='major bug'>
+    Working around a GZip compression bug in jzlib affecting transfer of certain large, repetitive artifacts.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-19473">issue 19473</a>)
 </ul>
 </div><!--=TRUNK-END=-->
 

core/src/main/java/hudson/FilePath.java

@@ -632,7 +632,12 @@ public final class FilePath implements Serializable {
                 }
             }
             public OutputStream compress(OutputStream out) throws IOException {
-                return new GZIPOutputStream(new BufferedOutputStream(out));
+                return new GZIPOutputStream(new BufferedOutputStream(out),
+                        // TODO JENKINS-19473 workaround; replace when jzlib fixed
+                        new com.jcraft.jzlib.Deflater(6, 15+16, 9),   // use 9 for memLevel
+                        512,
+                        true
+                );
             }
         };