expose the submitted file name

core/src/main/java/hudson/model/FileParameterDefinition.java

@@ -86,12 +86,21 @@ public class FileParameterDefinition extends ParameterDefinition {
             // the requested file parameter wasn't uploaded
             return null;
         }
-        FileParameterValue p = new FileParameterValue(getName(), src);
+        FileParameterValue p = new FileParameterValue(getName(), src, getFileName(src.getName()));
         p.setDescription(getDescription());
         p.setLocation(getName());
         return p;
 	}
 
+    /**
+     * Strip off the path portion if the given path contains it.
+     */
+    private String getFileName(String possiblyPathName) {
+        possiblyPathName = possiblyPathName.substring(possiblyPathName.lastIndexOf('/')+1);
+        possiblyPathName = possiblyPathName.substring(possiblyPathName.lastIndexOf('\\')+1);
+        return possiblyPathName;
+    }
+
     @Override
     public ParameterValue createValue(CLICommand command, String value) throws IOException, InterruptedException {
         // capture the file to the server

war/src/main/webapp/help/parameter/file.html

@@ -8,8 +8,17 @@
     place the file.</li>
     <li>Perform data processing by uploading a dataset.</li>
     </ol>
-    <p>It is possible to not submit any file. If it's case and if no file is
-    already present at the specified location in the workspace, then nothing
-    happens. If there's already a file present in the workspace, then this file
-    will be kept as-is.</p>
+    <p>
+        The name of the submitted file is available in the environment variable
+        whose name is the same as file location. For example, if you set the file
+        location to be <tt>abc.zip</tt>, then <tt>${abc.zip}</tt> would give you
+        the original file name passed from the browser (such as <tt>my.zip</tt>.)
+        The name will not include the directory name portion.
+    </p>
+    <p>
+        File upload is optional. If a user chooses not to upload anything,
+        Jenkins will simply skips this parameter and will not place
+        anything (but it also will not delete anything that's already in the
+        workspace.)
+    </p>
 </div>
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