Add skipemptyfilesets attributes to <execon> and <apply>.

PR: 1277


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@269038 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/CoreTasks/apply.html

@@ -71,6 +71,13 @@ one mapper element are required.</p>
       variables are specified.</td>
     <td align="center" valign="top">No, default is <i>false</i></td>
   </tr>
+  <tr>
+    <td valign="top">skipemptyfilesets</td>
+    <td valign="top">Don't run the command, if no source files have
+      been found or are newer than their corresponding target
+      files.</td>
+    <td align="center" valign="top">No, default is <i>false</i></td>
+  </tr>
   <tr>
     <td valign="top">parallel</td>
     <td valign="top">Run the command only once, appending all files as

src/main/org/apache/tools/ant/taskdefs/Chmod.java

@@ -77,6 +77,7 @@ public class Chmod extends ExecuteOn {
     public Chmod() {
         super.setExecutable("chmod");
         super.setParallel(true);
+        super.setSkipEmptyFilesets(true);
     }
 
     public void setFile(File src) {
@@ -194,6 +195,10 @@ public class Chmod extends ExecuteOn {
         throw new BuildException(taskType+" doesn\'t support the command attribute", location);
     }
 
+    public void setSkipEmptyFilesets(boolean skip) {
+        throw new BuildException(taskType+" doesn\'t support the skipemptyfileset attribute", location);
+    }
+
     protected boolean isValidOs() {
         // XXX if OS=unix
         return System.getProperty("path.separator").equals(":") 

src/main/org/apache/tools/ant/taskdefs/ExecuteOn.java

@@ -73,6 +73,7 @@ public class ExecuteOn extends ExecTask {
     private boolean parallel = false;
     protected String type = "file";
     protected Commandline.Marker srcFilePos = null;
+    private boolean skipEmpty = false;
 
     /**
      * Adds a set of files (nested fileset attribute).
@@ -95,6 +96,13 @@ public class ExecuteOn extends ExecTask {
         this.type = type.getValue();
     }
 
+    /**
+     * Should empty filesets be ignored?
+     */
+    public void setSkipEmptyFilesets(boolean skip) {
+        skipEmpty = skip;
+    }
+
     /**
      * Marker that indicates where the name of the source file should
      * be put on the command line.
@@ -138,6 +146,12 @@ public class ExecuteOn extends ExecTask {
                     }
                 }
 
+                if (v.size() == 0 && skipEmpty) {
+                    log("Skipping fileset for directory "
+                        + base + ". It is empty.", Project.MSG_INFO);
+                    continue;
+                }
+
                 String[] s = new String[v.size()];
                 v.copyInto(s);