tests: add additional test case for jj simplify-parents

This test shows that the current implementation of `jj simplify-parents`
perform unnecessary rebases of descendant commits.

cli/tests/test_simplify_parents_command.rs

@@ -157,7 +157,6 @@ fn test_simplify_parents_redundant_parent(args: &[&str]) {
     ◆
     "###);
     }
-
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, args);
     insta::allow_duplicates! {
     insta::assert_snapshot!(stdout, @"");
@@ -178,3 +177,78 @@ fn test_simplify_parents_redundant_parent(args: &[&str]) {
     "###);
     }
 }
+
+#[test]
+fn test_simplify_parents_multiple_redundant_parents() {
+    let (test_env, repo_path) = create_repo();
+
+    create_commit(&test_env, &repo_path, "a", &["root()"]);
+    create_commit(&test_env, &repo_path, "b", &["a"]);
+    create_commit(&test_env, &repo_path, "c", &["a", "b"]);
+    create_commit(&test_env, &repo_path, "d", &["c"]);
+    create_commit(&test_env, &repo_path, "e", &["d"]);
+    create_commit(&test_env, &repo_path, "f", &["d", "e"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "all()", "-T", "description"]);
+    insta::assert_snapshot!(stdout, @r#"
+    @    f
+    ├─╮
+    │ ○  e
+    ├─╯
+    ○  d
+    ○    c
+    ├─╮
+    │ ○  b
+    ├─╯
+    ○  a
+    ◆
+    "#);
+    let setup_opid = test_env.current_operation_id(&repo_path);
+
+    // Test with `-r`.
+    let (stdout, stderr) =
+        test_env.jj_cmd_ok(&repo_path, &["simplify-parents", "-r", "c", "-r", "f"]);
+    insta::assert_snapshot!(stdout, @"");
+    // TODO: The output should indicate that edges were removed from 2 commits
+    // (c, f) and 2 descendant commits were rebased (d, e).
+    insta::assert_snapshot!(stderr, @r#"
+    Removed 2 edges from 2 out of 2 commits.
+    Rebased 3 descendant commits
+    Working copy now at: kmkuslsw 8cc01e1b f | f
+    Parent commit      : znkkpsqq 040ae3a6 e | e
+    "#);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "all()", "-T", "description"]);
+    insta::assert_snapshot!(stdout, @r#"
+    @  f
+    ○  e
+    ○  d
+    ○  c
+    ○  b
+    ○  a
+    ◆
+    "#);
+
+    // Test with `-s`.
+    test_env.jj_cmd_ok(&repo_path, &["op", "restore", &setup_opid]);
+    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["simplify-parents", "-s", "c"]);
+    insta::assert_snapshot!(stdout, @"");
+    // TODO: The output should indicate that edges were removed from 2 commits
+    // (c, f) and 2 descendant commits were rebased (d, e).
+    insta::assert_snapshot!(stderr, @r#"
+    Removed 2 edges from 2 out of 4 commits.
+    Rebased 3 descendant commits
+    Working copy now at: kmkuslsw 70a39dff f | f
+    Parent commit      : znkkpsqq a021fee9 e | e
+    "#);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "all()", "-T", "description"]);
+    insta::assert_snapshot!(stdout, @r#"
+    @  f
+    ○  e
+    ○  d
+    ○  c
+    ○  b
+    ○  a
+    ◆
+    "#);
+}