Take nonewline context into account in diff parser

What does this MR do?

The problem is that the parser doesn’t check which file doesn’t have no newline, it only check that there's a nonewline and add it for both sides of the diff.

My approach to fix this was to replace nonewline with old-nonewline and new-nonewline based on context.

This takes into assumption that no diff will have \ No newline at end of file before any changes.

The conflict parser also uses nonewline. I’ll update it but I need to make sure that my approach to fix this problem is good.

Update:

As I've tested, the conflict parser will not be affected by the nonewline problem.

These scenarios need to be tested / asserted:

• a doesn’t have new line but b does.

• a have new line but b doesn’t.

• a doesn’t have new line and b doesn’t.

• a have new line and b does.

Are there points in the code the reviewer needs to double check?

Screenshots (if relevant)

Currently the diff looks like this for the different scenarios:

1- a doesn’t have new line but b does.

this branch	master 2d006b46

diff:

$ git diff 3...4
diff --git a/d b/d
index 2e65efe..6178079 100644
--- a/d
+++ b/d
@@ -1 +1 @@
-a
\ No newline at end of file
+b

2- a have new line but b doesn’t.

this branch	master 2d006b46

diff:

$ git diff master...t
diff --git a/a b/a
index 7898192..63d8dbd 100644
--- a/a
+++ b/a
@@ -1 +1 @@
-a
+b
\ No newline at end of file

3- a doesn’t have new line and b doesn’t.

this branch	master 2d006b46

diff:

$ git diff master...b
diff --git a/a b/a
index 2e65efe..63d8dbd 100644
--- a/a
+++ b/a
@@ -1 +1 @@
-a
\ No newline at end of file
+b
\ No newline at end of file

4-a have new line and b does.

this branch	master 2d006b46

diff:

$ git diff 1...2
diff --git a/test b/test
index 7187db3..304d8aa 100644
--- a/test
+++ b/test
@@ -1,2 +1,2 @@
-lorem
 ipsum
+lorem

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #28128 (closed)

Closes #22636 (closed)