fix(amazonq): Improved LLM code review for file review #6162

## Problem
- Code diff for file review format has changed in payload to improve LLM
based code review accuracy and is dependent on git.

## Solution
- We are currently send entire file in diff format and run git commands
to extract it. This change will remove git dependency for LLM based code
review issues.

Author: ashishrp-aws

packages/amazonq/.changes/next-release/Bug Fix-0c35b577-da17-4132-a0b7-e0d630e73cb9.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "Improved LLM code review for file review."
+}

packages/core/src/codewhisperer/util/zipUtil.ts

@@ -122,12 +122,8 @@ export class ZipUtil {
             zip.addFile(zipEntryPath, Buffer.from(content, 'utf-8'))
 
             if (scope === CodeWhispererConstants.CodeAnalysisScope.FILE_ON_DEMAND) {
-                await this.processCombinedGitDiff(
-                    zip,
-                    [workspaceFolder.uri.fsPath],
-                    uri.fsPath,
-                    CodeWhispererConstants.CodeAnalysisScope.FILE_ON_DEMAND
-                )
+                const gitDiffContent = `+++ b/${path.normalize(zipEntryPath)}` // Sending file path in payload for LLM code review
+                zip.addFile(ZipConstants.codeDiffFilePath, Buffer.from(gitDiffContent, 'utf-8'))
             }
         } else {
             zip.addFile(uri.fsPath, Buffer.from(content, 'utf-8'))