fix: Only select diff lines

[valentindeaconu]

Fixes #28.

We can pass the --unified=0 argument to the git diff command to only return actual diffs, without any contextual lines before and after. The action doesn't really need to select lines before and after the suggestion since the suggestion is annotated in GitHub and users can view the exact location of the changes in the UI.

This fixes the problem where the suggestion contains lines that are not part of the diff.

---

Example index.js

     1	const SOME_VARIABLE = "test";
     2	const SOME_OTHER_VARIABLE_TO_ADD_LINES = "new-test";
     3
     4	export function main(args) {
     5	  console.log("Hello, World!");
     6	}
     7
     8	function foo() {
     9	  console.log("foo");
    10	  console.log("bar");
    11	  console.log("baz");
    12	}
    13
    14	function bar() {
    15	  console.log("baz");
    16	  console.log("bar");
    17	  console.log("foo");
    18	}

Line deletion output

If we want to delete the line 9, git diff will output:

diff --git a/index.js b/index.js
index e7fad5537..bfe5e5fff 100644
--- a/index.js
+++ b/index.js
@@ -6,7 +6,6 @@ export function main(args) {
 }

 function foo() {
-  console.log("foo");
   console.log("bar");
   console.log("baz");
 }

while git diff --unified=0 will output:

diff --git a/index.js b/index.js
index e7fad5537..bfe5e5fff 100644
--- a/index.js
+++ b/index.js
@@ -9 +8,0 @@ function foo() {
-  console.log("foo");

Line addition output

If we want to add a line above the line 9, git diff will output:

diff --git a/index.js b/index.js
index e7fad5537..2c4768e93 100644
--- a/index.js
+++ b/index.js
@@ -6,6 +6,7 @@ export function main(args) {
 }

 function foo() {
+  console.log("foo");
   console.log("foo");
   console.log("bar");
   console.log("baz");

while git diff --unified=0 will output:

diff --git a/index.js b/index.js
index e7fad5537..2c4768e93 100644
--- a/index.js
+++ b/index.js
@@ -8,0 +9 @@ function foo() {
+  console.log("foo");

Line modification output

If we want to change the line 9, git diff will output:

diff --git a/index.js b/index.js
index e7fad5537..5a7c6f20e 100644
--- a/index.js
+++ b/index.js
@@ -6,7 +6,7 @@ export function main(args) {
 }

 function foo() {
-  console.log("foo");
+  console.log("oof");
   console.log("bar");
   console.log("baz");
 }

while git diff --unified=0 will output:

diff --git a/index.js b/index.js
index e7fad5537..5a7c6f20e 100644
--- a/index.js
+++ b/index.js
@@ -9 +9 @@ function foo() {
-  console.log("foo");
+  console.log("oof");

[parkerbxyz]

Thank you, @valentindeaconu! ✨