Change CopyFile routine

Author: facchinm

src/arduino.cc/builder/builder_utils/utils.go

@@ -414,63 +414,47 @@ func RemoveHyphenMDDFlagFromGCCCommandLine(buildProperties properties.Map) {
 	buildProperties[constants.BUILD_PROPERTIES_COMPILER_CPP_FLAGS] = strings.Replace(buildProperties[constants.BUILD_PROPERTIES_COMPILER_CPP_FLAGS], "-MMD", "", -1)
 }
 
-// CopyFile copies a file from src to dst. If src and dst files exist, and are
-// the same, then return success. Otherise, attempt to create a hard link
-// between the two files. If that fail, copy the file contents from src to dst.
-func CopyFile(src, dst string) (err error) {
-	sfi, err := os.Stat(src)
-	if err != nil {
-		return
-	}
-	if !sfi.Mode().IsRegular() {
-		// cannot copy non-regular files (e.g., directories,
-		// symlinks, devices, etc.)
-		return fmt.Errorf("CopyFile: non-regular source file %s (%q)", sfi.Name(), sfi.Mode().String())
-	}
-	dfi, err := os.Stat(dst)
-	if err != nil {
-		if !os.IsNotExist(err) {
-			return
-		}
-	} else {
-		if !(dfi.Mode().IsRegular()) {
-			return fmt.Errorf("CopyFile: non-regular destination file %s (%q)", dfi.Name(), dfi.Mode().String())
-		}
-		if os.SameFile(sfi, dfi) {
-			return
-		}
-	}
-	if err = os.Link(src, dst); err == nil {
-		return
-	}
-	err = copyFileContents(src, dst)
-	return
-}
-
-// copyFileContents copies the contents of the file named src to the file named
+// CopyFile copies the contents of the file named src to the file named
 // by dst. The file will be created if it does not already exist. If the
 // destination file exists, all it's contents will be replaced by the contents
-// of the source file.
-func copyFileContents(src, dst string) (err error) {
+// of the source file. The file mode will be copied from the source and
+// the copied data is synced/flushed to stable storage.
+func CopyFile(src, dst string) (err error) {
 	in, err := os.Open(src)
 	if err != nil {
 		return
 	}
 	defer in.Close()
+
 	out, err := os.Create(dst)
 	if err != nil {
 		return
 	}
 	defer func() {
-		cerr := out.Close()
-		if err == nil {
-			err = cerr
+		if e := out.Close(); e != nil {
+			err = e
 		}
 	}()
-	if _, err = io.Copy(out, in); err != nil {
+
+	_, err = io.Copy(out, in)
+	if err != nil {
 		return
 	}
+
 	err = out.Sync()
+	if err != nil {
+		return
+	}
+
+	si, err := os.Stat(src)
+	if err != nil {
+		return
+	}
+	err = os.Chmod(dst, si.Mode())
+	if err != nil {
+		return
+	}
+
 	return
 }