From 25ca3de5fc6b95b6cb0645f8ca16e4722d7e56b4 Mon Sep 17 00:00:00 2001
From: kohsuke <kohsuke@71c3de6d-444a-0410-be80-ed276b4c234a>
Date: Mon, 21 Sep 2009 23:52:09 +0000
Subject: [PATCH] Update center will create backup files to make it easier for
 manual roll back of botched upgrades.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@21980 71c3de6d-444a-0410-be80-ed276b4c234a
---
 core/src/main/java/hudson/Util.java               | 13 +++++++++++++
 core/src/main/java/hudson/model/UpdateCenter.java |  5 ++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/hudson/Util.java b/core/src/main/java/hudson/Util.java
index b9e4ec22b9..d2a0fab5ca 100644
--- a/core/src/main/java/hudson/Util.java
+++ b/core/src/main/java/hudson/Util.java
@@ -1044,6 +1044,19 @@ public class Util {
         }
     }
 
+    /**
+     * Returns a file name by changing its extension.
+     *
+     * @param ext
+     *      For example, ".zip"
+     */
+    public static File changeExtension(File dst, String ext) {
+        String p = dst.getPath();
+        int pos = p.lastIndexOf('.');
+        if (pos<0)  return new File(p+ext);
+        else        return new File(p.substring(0,pos)+ext);
+    }
+
     public static final FastDateFormat XS_DATETIME_FORMATTER = FastDateFormat.getInstance("yyyy-MM-dd'T'HH:mm:ss'Z'",new SimpleTimeZone(0,"GMT"));
 
     // Note: RFC822 dates must not be localized!
diff --git a/core/src/main/java/hudson/model/UpdateCenter.java b/core/src/main/java/hudson/model/UpdateCenter.java
index 6b6126e260..cee7dfc271 100644
--- a/core/src/main/java/hudson/model/UpdateCenter.java
+++ b/core/src/main/java/hudson/model/UpdateCenter.java
@@ -835,7 +835,10 @@ public class UpdateCenter extends AbstractModelObject {
          * the old file with the new file.
          */
         protected void replace(File dst, File src) throws IOException {
-            dst.delete();
+            File bak = Util.changeExtension(dst,".bak");
+            bak.delete();
+            dst.renameTo(bak);
+            dst.delete(); // any failure up to here is no big deal
             if(!src.renameTo(dst)) {
                 throw new IOException("Failed to rename "+src+" to "+dst);
             }