delete existing target files before copying - this avoids overwriting

symlinks and is consistent with Unix's cp(1).

PR: 624
Submitted by:	ederksen@arrow.lz.att.com (Enno Derksen)


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@269267 13f79535-47bb-0310-9956-ffa450edef68

WHATSNEW

@@ -139,6 +139,9 @@ Fixed bugs:
 * <jjtree>'s uptodate test works even if outputdirectory is not the
   parent dir of target
 
+* <copy> will remove target file (if it exists) before writing to it -
+  this avoids problems with links on filesystems that support them.
+
 Changes from Ant 1.2 to Ant 1.3
 ===========================================
 

src/main/org/apache/tools/ant/Project.java

@@ -752,8 +752,13 @@ public class Project {
                          boolean overwrite, boolean preserveLastModified)
         throws IOException {
         
-        if (overwrite ||
+        if (overwrite || !destFile.exists() ||
             destFile.lastModified() < sourceFile.lastModified()) {
+
+            if (destFile.exists()) {
+                destFile.delete();
+            }
+
             log("Copy: " + sourceFile.getAbsolutePath() + " -> "
                     + destFile.getAbsolutePath(), MSG_VERBOSE);