Conflicted File Missing Diff and Content in Conflict State

[Smart-SangGe]

Describe the bug
When a merge conflict occurs, GitUI fails to display the conflict markers or the diff for the conflicted file. Instead of showing the diff (e.g., between HEAD and the incoming branch), the diff view appears blank or displays an incorrect file size, making it difficult to resolve conflicts within the UI.

To Reproduce
Steps to reproduce the behavior:

1. Initialize a Git repository.
2. Create file.txt with "Original Line" on master.
3. Create branch feature from master.
4. On master, change file.txt to "Master Line" and commit.
5. On feature, change file.txt to "Feature Line" and commit.
6. On master, run git merge feature to trigger a conflict.
7. Open gitui.
8. Navigate to the "Status" tab and select the conflicted file.txt.
9. Observe that the diff view is blank or incorrect.

Expected behavior
GitUI should correctly display the conflict markers (e.g., <<<<<<<, =======, >>>>>>>) and provide a diff view that allows the user to see the differences between branches and ideally use the "Stage" or "Resolve" functions.

Screenshots

Context

• OS/Distro + Version: Linux localhost 6.12.38+kali-amd64 #1 SMP PREEMPT_DYNAMIC Kali 6.12.38-1kali1 (2025-08-12) x86_64 GNU/Linux
• GitUI Version: gitui nightly 2025-12-15
• Rust version: rustc 1.93.1 (01f6ddf75 2026-02-11)

Additional context
Current Git state and file content for reference:

Git Status

On branch master
You have unmerged paths.
  (fix conflicts and run "git commit")
  (use "git merge --abort" to abort the merge)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   file.txt

File Content (file.txt)

<<<<<<< HEAD
Master Line
=======
Feature Line
>>>>>>> feature

Git Diff

diff --cc file.txt
index 8ba2485,60a7231..0000000
--- a/file.txt
+++ b/file.txt
@@@ -1,1 -1,1 +1,5 @@@
++<<<<<<< HEAD
 +Master Line
++=======
+ Feature Line
++>>>>>>> feature