Initial steps to be less aggressive overwriting kobalt-wrapper.jar.

modules/wrapper/src/main/java/com/beust/kobalt/wrapper/Main.java

@@ -143,7 +143,9 @@ public class Main {
         return System.getProperty("os.name").contains("Windows");
     }
 
-    private static final String[] FILES = new String[] { KOBALTW, "kobalt/wrapper/" + FILE_NAME + "-wrapper.jar" };
+    private static final String OUT_DIR = "kobalt/wrapper/";
+    private static final String[] FILES = new String[] { KOBALTW, OUT_DIR + FILE_NAME + "-wrapper.jar" };
+    private static final String VERSION_TXT = "wrapper-version.txt";
 
     private Path installDistribution() throws IOException {
         String wrapperVersion;
@@ -195,12 +197,29 @@ public class Main {
             }
         }
 
+        //
+        // If the user didn't specify --noOverwrite, compare the installed wrapper to the one
+        // we're trying to install and if they are the same, no need to overwrite
+        if (! noOverwrite) {
+            try (FileReader fw = new FileReader(new File(OUT_DIR, VERSION_TXT))) {
+                try (BufferedReader bw = new BufferedReader(fw)) {
+                    String installedVersion = bw.readLine();
+                    if (! wrapperVersion.equals(installedVersion)) {
+                        log(2, "  Trying to install a different version " + wrapperVersion + " != " + installedVersion
+                                + ", overwriting the installed wrapper");
+                    } else {
+                        log(2, "  Trying to install the same version " + wrapperVersion + " == " + installedVersion
+                                + ", not overwriting the installed wrapper");
+                    }
+                }
+            }
+
+        }
+
         //
         // Copy the wrapper files in the current kobalt/wrapper directory
         //
-
         if (! noOverwrite) {
-            log(2, "Copying the wrapper files");
              for (String file : FILES) {
                 Path to = Paths.get(file);
                 to.toFile().getAbsoluteFile().getParentFile().mkdirs();
@@ -213,6 +232,7 @@ public class Main {
                         if (isWindows() && to.toFile().exists()) {
                             log(2, "  Windows detected, not overwriting " + to);
                         } else {
+                            log(2, "  Writing " + to);
                             Files.copy(from, to, StandardCopyOption.REPLACE_EXISTING);
                         }
                     } catch (IOException ex) {
@@ -220,6 +240,16 @@ public class Main {
                     }
                 }
             }
+
+            //
+            // Save wrapper-version.txt
+            //
+            log(2, "  Writing version.txt");
+            try (FileWriter fw = new FileWriter(new File(OUT_DIR, VERSION_TXT))) {
+                try (BufferedWriter bw = new BufferedWriter(fw)) {
+                    bw.write(wrapperVersion);
+                }
+            }
         }
 
         return kobaltJarFile;