refine ui

restore in a Dialog

src-tauri/src/git.rs

@@ -753,6 +753,66 @@ pub fn diff_file_against_working_tree(
     })
 }
 
+#[tauri::command]
+pub fn compare_file_to_head(
+    path: String,
+    commit: String,
+    file: String,
+) -> Result<GitCommitComparison, String> {
+    let repo = resolve_repo(&path)?;
+    validate_files(std::slice::from_ref(&file))?;
+    let commit_hash = verify_commit(&repo, &commit)?;
+    let head_hash = verify_commit(&repo, "HEAD")?;
+
+    let name_status = run_git_with_paths(
+        &repo,
+        &[
+            "diff",
+            "--name-status",
+            "-M",
+            "-z",
+            commit_hash.as_str(),
+            head_hash.as_str(),
+        ],
+        std::slice::from_ref(&file),
+    )?;
+    let numstat = run_git_with_paths(
+        &repo,
+        &[
+            "diff",
+            "--numstat",
+            "-M",
+            "-z",
+            commit_hash.as_str(),
+            head_hash.as_str(),
+        ],
+        std::slice::from_ref(&file),
+    )?;
+    let patch_output = run_git_with_paths(
+        &repo,
+        &[
+            "diff",
+            "-M",
+            FULL_FILE_DIFF_CONTEXT,
+            commit_hash.as_str(),
+            head_hash.as_str(),
+        ],
+        std::slice::from_ref(&file),
+    )?;
+
+    let files = parse_diff_files(&name_status, &numstat)?;
+    let patch = String::from_utf8_lossy(&patch_output).to_string();
+
+    Ok(GitCommitComparison {
+        from_short: short_hash(&commit_hash),
+        to_short: "HEAD".to_string(),
+        from_hash: commit_hash,
+        to_hash: head_hash,
+        files,
+        patch,
+    })
+}
+
 #[tauri::command]
 pub fn read_conflict(path: String, file: String) -> Result<ConflictFile, String> {
     let repo = resolve_repo(&path)?;
@@ -2497,6 +2557,35 @@ mod tests {
         assert!(comparison.patch.contains("working tree change"));
     }
 
+    #[test]
+    fn compare_file_to_head_reports_selected_file_against_current_commit() {
+        let repo = init_temp_repo("compare_file_to_head");
+        commit_initial_file(&repo.path);
+        let first_commit = git_output_test(&repo.path, ["rev-parse", "HEAD"]);
+
+        fs::write(repo.path.join("old.txt"), "original\nsecond line\n")
+            .expect("tracked file should change");
+        fs::write(repo.path.join("other.txt"), "other file\n")
+            .expect("other file should be written");
+        run_git_test(&repo.path, ["add", "old.txt", "other.txt"]);
+        run_git_test(&repo.path, ["commit", "-q", "-m", "second"]);
+        let head_commit = git_output_test(&repo.path, ["rev-parse", "HEAD"]);
+
+        let comparison = compare_file_to_head(
+            repo.path.to_string_lossy().to_string(),
+            first_commit,
+            "old.txt".to_string(),
+        )
+        .unwrap();
+
+        assert_eq!(comparison.to_hash, head_commit);
+        assert_eq!(comparison.to_short, "HEAD");
+        assert_eq!(comparison.files.len(), 1);
+        assert_eq!(comparison.files[0].path, "old.txt");
+        assert!(comparison.patch.contains("second line"));
+        assert!(!comparison.patch.contains("other file"));
+    }
+
     #[test]
     fn read_and_resolve_conflict_round_trip() {
         let repo = init_temp_repo("resolve_conflict");