merge_tools: simplify and deduplicate file conflicts before attemptin…

…g to resolve

cli/src/merge_tools/mod.rs

@@ -298,6 +298,7 @@ impl MergeEditor {
                 String::from_utf8_lossy(summary_bytes.as_slice()).to_string(),
             )
         })?;
+        let file_merge = file_merge.deduplicate().simplify();
         // We only support conflicts with 2 sides (3-way conflicts)
         if file_merge.num_sides() > 2 {
             return Err(ConflictResolveError::ConflictTooComplicated {

cli/tests/test_resolve_command.rs

@@ -491,7 +491,7 @@ fn test_too_many_parents() {
 
 #[test]
 fn test_simplify_conflict_sides() {
-    let test_env = TestEnvironment::default();
+    let mut test_env = TestEnvironment::default();
     test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
     let repo_path = test_env.env_root().join("repo");
 
@@ -552,13 +552,63 @@ fn test_simplify_conflict_sides() {
     >>>>>>> Conflict 1 of 1 ends
     "###);
 
-    // TODO: The conflict should be simplified before being resolved.
-    let error = test_env.jj_cmd_failure(&repo_path, &["resolve"]);
-    insta::assert_snapshot!(error, @r###"
-    Hint: Using default editor ':builtin'; run `jj config set --user ui.merge-editor :builtin` to disable this message.
-    Resolving conflicts in: file1
-    Error: Failed to resolve conflicts
-    Caused by: The conflict at "file1" has 3 sides. At most 2 sides are supported.
+    check_resolve_produces_input_file(&mut test_env, &repo_path, "file1", "base", "base\n");
+    check_resolve_produces_input_file(&mut test_env, &repo_path, "file1", "left", "a\n");
+    check_resolve_produces_input_file(&mut test_env, &repo_path, "file1", "right", "b\n");
+    // Manually resolve conflict in file 1.
+    std::fs::write(repo_path.join("file1"), "resolved").unwrap();
+    check_resolve_produces_input_file(&mut test_env, &repo_path, "file2", "base", "base\n");
+    check_resolve_produces_input_file(&mut test_env, &repo_path, "file2", "left", "a\n");
+    check_resolve_produces_input_file(&mut test_env, &repo_path, "file2", "right", "b\n");
+
+    // Check that simplified conflicts are still parsed as conflicts after editing
+    // when `merge-tool-edits-conflict-markers=true`.
+    let editor_script = test_env.set_up_fake_editor();
+    std::fs::write(
+        &editor_script,
+        indoc! {"
+            write
+            <<<<<<< Conflict 1 of 1
+            %%%%%%% Changes from base to side #1
+            -base_edited
+            +a_edited
+            +++++++ Contents of side #2
+            b_edited
+            >>>>>>> Conflict 1 of 1 ends
+        "},
+    )
+    .unwrap();
+    let (stdout, stderr) = test_env.jj_cmd_ok(
+        &repo_path,
+        &[
+            "resolve",
+            "--config-toml",
+            "merge-tools.fake-editor.merge-tool-edits-conflict-markers=true",
+        ],
+    );
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @r###"
+    Resolving conflicts in: file2
+    Working copy now at: znkkpsqq c19e4299 conflict | (conflict) conflict
+    Parent commit      : zsuskuln bd4692d0 a | a
+    Parent commit      : royxmykx c4337af0 b | b
+    Parent commit      : vruxwmqv 470d63cc c | c
+    Added 0 files, modified 1 files, removed 0 files
+    There are unresolved conflicts at these paths:
+    file2    2-sided conflict
+    "###);
+    insta::assert_snapshot!(std::fs::read_to_string(repo_path.join("file2")).unwrap(), @r###"
+    <<<<<<< Conflict 1 of 1
+    %%%%%%% Changes from base to side #1
+    -base_edited
+    +a_edited
+    +++++++ Contents of side #2
+    b_edited
+    >>>>>>> Conflict 1 of 1 ends
+    "###);
+    insta::assert_snapshot!(test_env.jj_cmd_success(&repo_path, &["resolve", "--list"]),
+    @r###"
+    file2    2-sided conflict
     "###);
 }