Fixes #642 Only add -d once to formatflags (#644)

Author: OneOfOne

src/goFormat.ts

@@ -29,7 +29,7 @@ export class Formatter {
 			let formatCommandBinPath = getBinPath(this.formatCommand);
 			let formatFlags = vscode.workspace.getConfiguration('go')['formatFlags'] || [];
 			let canFormatToolUseDiff = vscode.workspace.getConfiguration('go')['useDiffForFormatting'] && isDiffToolAvailable();
-			if (canFormatToolUseDiff) {
+			if (canFormatToolUseDiff && formatFlags.indexOf('-d') === -1) {
 				formatFlags.push('-d');
 			}
 			// We ignore the -w flag that updates file on disk because that would break undo feature
@@ -80,4 +80,4 @@ export class GoDocumentFormattingEditProvider implements vscode.DocumentFormatti
 
 // package main; import \"fmt\"; func main() {fmt.Print(\"Hello\")}
 // package main; import \"fmt\"; import \"math\"; func main() {fmt.Print(\"Hello\")}
-// package main; import \"fmt\"; import \"gopkg.in/Shopify/sarama.v1\"; func main() {fmt.Print(sarama.V0_10_0_0)}
+// package main; import \"fmt\"; import \"gopkg.in/Shopify/sarama.v1\"; func main() {fmt.Print(sarama.V0_10_0_0)}