clarify that old hunk was replaced (#180)

<!-- This is an auto-generated comment: release notes by openai -->
### Summary by OpenAI

Release Notes:

- Refactor: Update code review instructions and response format for
clarity and consistency.

> "Code review made easy,
> Instructions clear, response format breezy.
> Bugs and issues, we'll catch them all,
> Thanks to this PR, we stand tall."
<!-- end of auto-generated comment: release notes by openai -->

action.yml

@@ -118,7 +118,7 @@ inputs:
       $description
       ```
 
-      Content of file `$filename`:
+      Content of file `$filename` prior to changes:
       ```
       $file_content
       ```
@@ -181,7 +181,7 @@ inputs:
       $summary
       ```
 
-      Content of file `$filename` for context:
+      Content of `$filename` prior to changes for context:
       ```
       $file_content
       ```
@@ -209,7 +209,7 @@ inputs:
       $summary
       ```
 
-      Content of file:
+      Content of file prior to changes:
       ```
       $file_content
       ```

src/review.ts

@@ -146,12 +146,12 @@ export const codeReview = async (
           continue
         }
         const hunks_str = `
----new_hunk_for_review---
+---new_hunk---
 \`\`\`
 ${hunks.new_hunk}
 \`\`\`
 
----old_hunk_for_context---
+---old_hunk---
 \`\`\`
 ${hunks.old_hunk}
 \`\`\`
@@ -387,17 +387,17 @@ ${
     // Pack instructions
     ins.patches += `
 Format for changes:
-  ---new_hunk_for_review---
+  ---new_hunk---
   \`\`\`
   <new hunk annotated with line numbers>
   \`\`\`
 
-  ---old_hunk_for_context---
+  ---old_hunk---
   \`\`\`
   <old hunk that was replaced by the new hunk above>
   \`\`\`
 
-  ---comment_chains_for_context---
+  ---comment_chains---
   \`\`\`
   <comment chains>
   \`\`\`
@@ -406,9 +406,11 @@ Format for changes:
   ...
 
 The above format for changes consists of multiple change sections. 
-Each change section consists of a new hunk (annotated with line numbers), 
-an old hunk (that was replaced with new hunk) and optionally, comment 
-chains for context.
+Each change section consists of a new hunk (annotated with line numbers) 
+and an old hunk. Note that the code in old_hunk does not exist anymore
+as it was replaced by the new hunk. The old_hunk is only included for
+context. The new hunk is the code that you should review. Optionally, 
+existing review comment chains are included for additional context. 
 
 Important instructions:
 - Your task is to do a line by line review of new hunks and point out 
@@ -434,7 +436,7 @@ Important instructions:
 - If needed, provide a replacement suggestion using fenced code blocks 
   with the \`suggestion\` as the language identifier. The line number range 
   in the review section must map exactly to the line number range (inclusive) 
-  that need to be replaced within a new_hunk_for_review.
+  that need to be replaced within a new_hunk.
   For instance, if 2 lines of code in a hunk need to be replaced with 15 lines 
   of code, the line number range must be those exact 2 lines. If an entire hunk 
   need to be replaced with new code, then the line number range must be the 
@@ -474,15 +476,15 @@ Response format expected:
   ...
 
 Example changes:
-  ---new_hunk_for_review---
+  ---new_hunk---
   1: def add(x, y):
   2:     z = x+y
   3:     retrn z
   4:
   5: def multiply(x, y):
   6:     return x * y
   
-  ---old_hunk_for_context---
+  ---old_hunk---
   def add(x, y):
       return x + y
 
@@ -577,7 +579,7 @@ ${patch}
 `
       if (comment_chain !== '') {
         ins.patches += `
----comment_chains_for_review---
+---comment_chains---
 \`\`\`
 ${comment_chain}
 \`\`\`