revset: convert root symbol to function

The idea is that we can fully eliminate special symbols that would otherwise
shadow user branches, tags, or change ID prefixes.

Closes #2095

CHANGELOG.md

@@ -50,6 +50,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   parameters. For example, `author(foo@)` is now an error, and the revset alias
   `'revset-aliases.foo@' = '@'` will be failed to parse.
 
+* The `root` revset symbol has been converted to function `root()`.
+
 * `jj git push` will now push all branches in the range `remote_branches()..@`
   instead of only branches pointing to `@` or `@-`.
 

cli/src/config/templates.toml

@@ -115,7 +115,7 @@ builtin_op_log_comfortable = 'builtin_op_log_compact ++ "\n"'
 'builtin_log_root(change_id, commit_id)' = '''
 separate(" ",
   format_short_change_id(change_id),
-  label("root", "root"),
+  label("root", "root()"),
   format_short_commit_id(commit_id),
   branches
 )

cli/tests/test_abandon_command.rs

@@ -20,7 +20,7 @@ pub mod common;
 
 fn create_commit(test_env: &TestEnvironment, repo_path: &Path, name: &str, parents: &[&str]) {
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", name]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);
@@ -153,7 +153,7 @@ fn test_rebase_branch_with_merge() {
     ◉  a b e??
     "###);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["abandon", "root"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["abandon", "root()"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot rewrite the root commit
     "###);

cli/tests/test_alias.rs

@@ -135,9 +135,9 @@ fn test_alias_cannot_override_builtin() {
 
     test_env.add_config(r#"aliases.log = ["rebase"]"#);
     // Alias should be ignored
-    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "root"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "root()"]);
     insta::assert_snapshot!(stdout, @r###"
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 }
 

cli/tests/test_branch_command.rs

@@ -51,7 +51,7 @@ fn test_branch_forbidden_at_root() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["branch", "create", "fred", "-r=root"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["branch", "create", "fred", "-r=root()"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot rewrite the root commit
     "###);
@@ -448,7 +448,7 @@ fn test_branch_list_filtered_by_revset() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "remote", "--git"]);
     let remote_path = test_env.env_root().join("remote");
     for branch in ["remote-keep", "remote-delete", "remote-rewrite"] {
-        test_env.jj_cmd_success(&remote_path, &["new", "root", "-m", branch]);
+        test_env.jj_cmd_success(&remote_path, &["new", "root()", "-m", branch]);
         test_env.jj_cmd_success(&remote_path, &["branch", "set", branch]);
     }
     test_env.jj_cmd_success(&remote_path, &["new"]);
@@ -462,7 +462,7 @@ fn test_branch_list_filtered_by_revset() {
         &["git", "clone", remote_git_path.to_str().unwrap(), "local"],
     );
     let local_path = test_env.env_root().join("local");
-    test_env.jj_cmd_success(&local_path, &["new", "root", "-m", "local-keep"]);
+    test_env.jj_cmd_success(&local_path, &["new", "root()", "-m", "local-keep"]);
     test_env.jj_cmd_success(&local_path, &["branch", "set", "local-keep"]);
 
     // Mutate refs in local repository

cli/tests/test_checkout.rs

@@ -63,10 +63,10 @@ fn test_checkout_not_single_rev() {
     test_env.jj_cmd_success(&repo_path, &["commit", "-m", "fourth"]);
     test_env.jj_cmd_success(&repo_path, &["commit", "-m", "fifth"]);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["checkout", "root..@"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["checkout", "root()..@"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Revset "root..@" resolved to more than one revision
+    Error: Revset "root()..@" resolved to more than one revision
-    Hint: The revset "root..@" resolved to these revisions:
+    Hint: The revset "root()..@" resolved to these revisions:
     royxmykx 2f859371 (empty) (no description set)
     mzvwutvl 5c1afd8b (empty) fifth
     zsuskuln 009f88bf (empty) fourth
@@ -75,10 +75,10 @@ fn test_checkout_not_single_rev() {
     ...
     "###);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["checkout", "root..@-"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["checkout", "root()..@-"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Revset "root..@-" resolved to more than one revision
+    Error: Revset "root()..@-" resolved to more than one revision
-    Hint: The revset "root..@-" resolved to these revisions:
+    Hint: The revset "root()..@-" resolved to these revisions:
     mzvwutvl 5c1afd8b (empty) fifth
     zsuskuln 009f88bf (empty) fourth
     kkmpptxz 3fa8931e (empty) third

cli/tests/test_chmod_command.rs

@@ -26,7 +26,7 @@ fn create_commit(
     files: &[(&str, &str)],
 ) {
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", name]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);

cli/tests/test_commit_template.rs

@@ -141,7 +141,7 @@ fn test_log_default() {
     │  (empty) description 1
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:08.000 +07:00 4291e264
     │  add a file
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Color
@@ -151,7 +151,7 @@ fn test_log_default() {
     │  (empty) description 1
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:08.000 +07:00 4291e264
     │  add a file
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Color without graph
@@ -161,7 +161,7 @@ fn test_log_default() {
     (empty) description 1
     qpvuntsm test.user@example.com 2001-02-03 04:05:08.000 +07:00 4291e264
     add a file
-    zzzzzzzz root 00000000
+    zzzzzzzz root() 00000000
     "###);
 }
 
@@ -184,7 +184,7 @@ fn test_log_builtin_templates() {
     insta::assert_snapshot!(render(r#"builtin_log_oneline"#), @r###"
     @  rlvkpnrz (no email set) 2001-02-03 04:05:08.000 +07:00 dc315397 (empty) (no description set)
     ◉  qpvuntsm test.user 2001-02-03 04:05:07.000 +07:00 230dd059 (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     insta::assert_snapshot!(render(r#"builtin_log_compact"#), @r###"
@@ -192,7 +192,7 @@ fn test_log_builtin_templates() {
     │  (empty) (no description set)
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 230dd059
     │  (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     insta::assert_snapshot!(render(r#"builtin_log_comfortable"#), @r###"
@@ -202,7 +202,7 @@ fn test_log_builtin_templates() {
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 230dd059
     │  (empty) (no description set)
     │
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     insta::assert_snapshot!(render(r#"builtin_log_detailed"#), @r###"
@@ -250,7 +250,7 @@ fn test_log_builtin_templates_colored() {
     insta::assert_snapshot!(render(r#"builtin_log_oneline"#), @r###"
     @  rlvkpnrz (no email set) 2001-02-03 04:05:08.000 +07:00 dc315397 (empty) (no description set)
     ◉  qpvuntsm test.user 2001-02-03 04:05:07.000 +07:00 230dd059 (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     insta::assert_snapshot!(render(r#"builtin_log_compact"#), @r###"
@@ -258,7 +258,7 @@ fn test_log_builtin_templates_colored() {
     │  (empty) (no description set)
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 230dd059
     │  (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     insta::assert_snapshot!(render(r#"builtin_log_comfortable"#), @r###"
@@ -268,7 +268,7 @@ fn test_log_builtin_templates_colored() {
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 230dd059
     │  (empty) (no description set)
     │
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     insta::assert_snapshot!(render(r#"builtin_log_detailed"#), @r###"
@@ -309,7 +309,7 @@ fn test_log_obslog_divergence() {
     insta::assert_snapshot!(stdout, @r###"
     @  qpvuntsm test.user@example.com 2001-02-03 04:05:08.000 +07:00 7a17d52e
     │  description 1
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Create divergence
@@ -324,7 +324,7 @@ fn test_log_obslog_divergence() {
     │  description 2
     │ @  qpvuntsm?? test.user@example.com 2001-02-03 04:05:08.000 +07:00 7a17d52e
     ├─╯  description 1
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Color
@@ -334,7 +334,7 @@ fn test_log_obslog_divergence() {
     │  description 2
     │ @  qpvuntsm?? test.user@example.com 2001-02-03 04:05:08.000 +07:00 7a17d52e
     ├─╯  description 1
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Obslog and hidden divergent
@@ -375,7 +375,7 @@ fn test_log_git_head() {
     │  initial
     ◉  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 master HEAD@git 230dd059
     │  (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 }
 
@@ -400,7 +400,7 @@ fn test_log_customize_short_id() {
     insta::assert_snapshot!(stdout, @r###"
     @  Q_pvun test.user@example.com 2001-02-03 04:05:08.000 +07:00 6_9542
     │  (empty) first
-    ◉  Z_zzzz root 0_0000
+    ◉  Z_zzzz root() 0_0000
     "###);
 
     // Customize only the change id
@@ -418,6 +418,6 @@ fn test_log_customize_short_id() {
     insta::assert_snapshot!(stdout, @r###"
     @  QPVUNTSM test.user@example.com 2001-02-03 04:05:08.000 +07:00 69542c19
     │  (empty) first
-    ◉  ZZZZZZZZ root 00000000
+    ◉  ZZZZZZZZ root() 00000000
     "###);
 }

cli/tests/test_debug_command.rs

@@ -25,7 +25,7 @@ fn test_debug_revset() {
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let workspace_path = test_env.env_root().join("repo");
 
-    let stdout = test_env.jj_cmd_success(&workspace_path, &["debug", "revset", "root"]);
+    let stdout = test_env.jj_cmd_success(&workspace_path, &["debug", "revset", "root()"]);
     insta::with_settings!({filters => vec![
         (r"(?m)(^    .*\n)+", "    ..\n"),
     ]}, {

cli/tests/test_diff_command.rs

@@ -154,16 +154,16 @@ fn test_diff_types() {
     let file_path = repo_path.join("foo");
 
     // Missing
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=missing"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=missing"]);
 
     // Normal file
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=file"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=file"]);
     std::fs::write(&file_path, "foo").unwrap();
 
     // Conflict (add/add)
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=conflict"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=conflict"]);
     std::fs::write(&file_path, "foo").unwrap();
-    test_env.jj_cmd_success(&repo_path, &["new", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()"]);
     std::fs::write(&file_path, "bar").unwrap();
     test_env.jj_cmd_success(&repo_path, &["move", r#"--to=description("conflict")"#]);
 
@@ -173,12 +173,12 @@ fn test_diff_types() {
         use std::path::PathBuf;
 
         // Executable
-        test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=executable"]);
+        test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=executable"]);
         std::fs::write(&file_path, "foo").unwrap();
         std::fs::set_permissions(&file_path, std::fs::Permissions::from_mode(0o755)).unwrap();
 
         // Symlink
-        test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=symlink"]);
+        test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=symlink"]);
         std::os::unix::fs::symlink(PathBuf::from("."), &file_path).unwrap();
     }
 
@@ -689,7 +689,7 @@ fn test_diff_external_tool() {
     │  --
     │  file1
     │  file2
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
        --
     "###);
 
@@ -793,7 +793,7 @@ fn test_diff_stat_long_name_or_stat() {
     let repo_path = test_env.env_root().join("repo");
 
     let get_stat = |test_env: &TestEnvironment, path_length: usize, stat_size: usize| {
-        test_env.jj_cmd_success(&repo_path, &["new", "root"]);
+        test_env.jj_cmd_success(&repo_path, &["new", "root()"]);
         let ascii_name = "1234567890".chars().cycle().take(path_length).join("");
         let han_name = "一二三四五六七八九十"
             .chars()

cli/tests/test_duplicate_command.rs

@@ -20,7 +20,7 @@ pub mod common;
 
 fn create_commit(test_env: &TestEnvironment, repo_path: &Path, name: &str, parents: &[&str]) {
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", name]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);
@@ -49,7 +49,7 @@ fn test_duplicate() {
     ◉  000000000000
     "###);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["duplicate", "root"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["duplicate", "root()"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot rewrite the root commit
     "###);

cli/tests/test_edit_command.rs

@@ -116,6 +116,6 @@ fn test_edit_root() {
     let test_env = TestEnvironment::default();
     test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
     let repo_path = test_env.env_root().join("repo");
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["edit", "root"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["edit", "root()"]);
     insta::assert_snapshot!(stderr, @"Error: Cannot rewrite the root commit");
 }

cli/tests/test_git_colocated.rs

@@ -313,7 +313,7 @@ fn test_git_colocated_external_checkout() {
     let git_repo = git2::Repository::init(&repo_path).unwrap();
     test_env.jj_cmd_success(&repo_path, &["init", "--git-repo=."]);
     test_env.jj_cmd_success(&repo_path, &["ci", "-m=A"]);
-    test_env.jj_cmd_success(&repo_path, &["new", "-m=B", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "-m=B", "root()"]);
     test_env.jj_cmd_success(&repo_path, &["new"]);
 
     // Checked out anonymous branch

cli/tests/test_git_fetch.rs

@@ -58,7 +58,7 @@ fn get_branch_output(test_env: &TestEnvironment, repo_path: &Path) -> String {
 fn create_commit(test_env: &TestEnvironment, repo_path: &Path, name: &str, parents: &[&str]) {
     let descr = format!("descr_for_{name}");
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", &descr]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", &descr]);
     } else {
         let mut args = vec!["new", "-m", &descr];
         args.extend(parents);
@@ -299,7 +299,7 @@ fn test_git_fetch_conflicting_branches() {
     add_git_remote(&test_env, &repo_path, "rem1");
 
     // Create a rem1 branch locally
-    test_env.jj_cmd_success(&repo_path, &["new", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()"]);
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "rem1"]);
     insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
     rem1: kkmpptxz fcdbbd73 (empty) (no description set)
@@ -329,7 +329,7 @@ fn test_git_fetch_conflicting_branches_colocated() {
     insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @"");
 
     // Create a rem1 branch locally
-    test_env.jj_cmd_success(&repo_path, &["new", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()"]);
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "rem1"]);
     insta::assert_snapshot!(get_branch_output(&test_env, &repo_path), @r###"
     rem1: zsuskuln f652c321 (empty) (no description set)

cli/tests/test_git_push.rs

@@ -30,7 +30,7 @@ fn set_up() -> (TestEnvironment, PathBuf) {
 
     test_env.jj_cmd_success(&origin_path, &["describe", "-m=description 1"]);
     test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch1"]);
-    test_env.jj_cmd_success(&origin_path, &["new", "root", "-m=description 2"]);
+    test_env.jj_cmd_success(&origin_path, &["new", "root()", "-m=description 2"]);
     test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch2"]);
     test_env.jj_cmd_success(&origin_path, &["git", "export"]);
 
@@ -505,7 +505,7 @@ fn test_git_push_missing_author() {
             .assert()
             .success();
     };
-    run_without_var("JJ_USER", &["checkout", "root", "-m=initial"]);
+    run_without_var("JJ_USER", &["checkout", "root()", "-m=initial"]);
     run_without_var("JJ_USER", &["branch", "create", "missing-name"]);
     let stderr = test_env.jj_cmd_failure(
         &workspace_root,
@@ -514,7 +514,7 @@ fn test_git_push_missing_author() {
     insta::assert_snapshot!(stderr, @r###"
     Error: Won't push commit 944313939bbd since it has no author and/or committer set
     "###);
-    run_without_var("JJ_EMAIL", &["checkout", "root", "-m=initial"]);
+    run_without_var("JJ_EMAIL", &["checkout", "root()", "-m=initial"]);
     run_without_var("JJ_EMAIL", &["branch", "create", "missing-email"]);
     let stderr =
         test_env.jj_cmd_failure(&workspace_root, &["git", "push", "--branch=missing-email"]);
@@ -540,7 +540,7 @@ fn test_git_push_missing_committer() {
     insta::assert_snapshot!(stderr, @r###"
     Error: Won't push commit 4fd190283d1a since it has no author and/or committer set
     "###);
-    test_env.jj_cmd_success(&workspace_root, &["checkout", "root"]);
+    test_env.jj_cmd_success(&workspace_root, &["checkout", "root()"]);
     test_env.jj_cmd_success(&workspace_root, &["branch", "create", "missing-email"]);
     run_without_var("JJ_EMAIL", &["describe", "-m=no committer email"]);
     let stderr =
@@ -591,7 +591,7 @@ fn test_git_push_conflicting_branches() {
         .delete()
         .unwrap();
     test_env.jj_cmd_success(&workspace_root, &["git", "import"]);
-    test_env.jj_cmd_success(&workspace_root, &["new", "root", "-m=description 3"]);
+    test_env.jj_cmd_success(&workspace_root, &["new", "root()", "-m=description 3"]);
     test_env.jj_cmd_success(&workspace_root, &["branch", "set", "branch2"]);
     test_env.jj_cmd_success(&workspace_root, &["git", "fetch"]);
     insta::assert_snapshot!(test_env.jj_cmd_success(&workspace_root, &["branch", "list"]), @r###"

cli/tests/test_init_command.rs

@@ -321,7 +321,7 @@ fn test_init_git_external_but_git_dir_exists() {
     // The local ".git" repository is unrelated, so no commits should be imported
     let stdout = test_env.jj_cmd_success(&workspace_root, &["log", "-r", "@-"]);
     insta::assert_snapshot!(stdout, @r###"
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Check that Git HEAD is not set because this isn't a colocated repo

cli/tests/test_interdiff_command.rs

@@ -27,7 +27,7 @@ fn test_interdiff_basic() {
     std::fs::write(repo_path.join("file2"), "foo\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "left"]);
 
-    test_env.jj_cmd_success(&repo_path, &["checkout", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["checkout", "root()"]);
     std::fs::write(repo_path.join("file3"), "foo\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["new"]);
     std::fs::write(repo_path.join("file2"), "foo\nbar\n").unwrap();
@@ -91,7 +91,7 @@ fn test_interdiff_paths() {
     std::fs::write(repo_path.join("file2"), "bar\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "left"]);
 
-    test_env.jj_cmd_success(&repo_path, &["checkout", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["checkout", "root()"]);
     std::fs::write(repo_path.join("file1"), "foo\n").unwrap();
     std::fs::write(repo_path.join("file2"), "foo\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["new"]);
@@ -139,7 +139,7 @@ fn test_interdiff_conflicting() {
     std::fs::write(repo_path.join("file"), "bar\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "left"]);
 
-    test_env.jj_cmd_success(&repo_path, &["checkout", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["checkout", "root()"]);
     std::fs::write(repo_path.join("file"), "abc\n").unwrap();
     test_env.jj_cmd_success(&repo_path, &["new"]);
     std::fs::write(repo_path.join("file"), "def\n").unwrap();

cli/tests/test_log_command.rs

@@ -49,16 +49,16 @@ fn test_log_legacy_range_operator() {
     insta::assert_snapshot!(stdout, @r###"
     @  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 230dd059
     │  (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
     insta::assert_snapshot!(stderr, @r###"
     The `:` revset operator is deprecated. Please switch to `::`.
     "###);
-    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["log", "-r=root:@"]);
+    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["log", "-r=root():@"]);
     insta::assert_snapshot!(stdout, @r###"
     @  qpvuntsm test.user@example.com 2001-02-03 04:05:07.000 +07:00 230dd059
     │  (empty) (no description set)
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
     insta::assert_snapshot!(stderr, @r###"
     The `:` revset operator is deprecated. Please switch to `::`.
@@ -589,7 +589,7 @@ fn test_log_prefix_highlight_counts_hidden_commits() {
     );
 
     // Create 2^7 hidden commits
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m", "extra"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m", "extra"]);
     for _ in 0..7 {
         test_env.jj_cmd_success(&repo_path, &["duplicate", "description(extra)"]);
     }
@@ -954,7 +954,7 @@ fn test_default_revset() {
     test_env.jj_cmd_success(&repo_path, &["describe", "-m", "add a file"]);
 
     // Set configuration to only show the root commit.
-    test_env.add_config(r#"revsets.log = "root""#);
+    test_env.add_config(r#"revsets.log = "root()""#);
 
     // Log should only contain one line (for the root commit), and not show the
     // commit created above.
@@ -979,7 +979,7 @@ fn test_default_revset_per_repo() {
     // Set configuration to only show the root commit.
     std::fs::write(
         repo_path.join(".jj/repo/config.toml"),
-        r#"revsets.log = "root""#,
+        r#"revsets.log = "root()""#,
     )
     .unwrap();
 
@@ -1005,7 +1005,7 @@ fn test_multiple_revsets() {
     }
 
     // Default revset should be overridden if one or more -r options are specified.
-    test_env.add_config(r#"revsets.log = "root""#);
+    test_env.add_config(r#"revsets.log = "root()""#);
 
     insta::assert_snapshot!(
         test_env.jj_cmd_success(&repo_path, &["log", "-T", "branches", "-rfoo"]),

cli/tests/test_new_command.rs

@@ -34,7 +34,7 @@ fn test_new() {
     "###);
 
     // Start a new change off of a specific commit (the root commit in this case).
-    test_env.jj_cmd_success(&repo_path, &["new", "-m", "off of root", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "-m", "off of root", "root()"]);
     insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
     @  026537ddb96b801b9cb909985d5443aab44616c1 off of root
     │ ◉  4f2d6e0a3482a6a34e4856a4a63869c0df109e79 a new commit
@@ -53,7 +53,7 @@ fn test_new_merge() {
     test_env.jj_cmd_success(&repo_path, &["branch", "create", "main"]);
     test_env.jj_cmd_success(&repo_path, &["describe", "-m", "add file1"]);
     std::fs::write(repo_path.join("file1"), "a").unwrap();
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m", "add file2"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m", "add file2"]);
     std::fs::write(repo_path.join("file2"), "b").unwrap();
 
     // Create a merge commit
@@ -100,7 +100,7 @@ fn test_new_merge() {
     "###);
 
     // merge with root
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["new", "@", "root"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["new", "@", "root()"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot merge with root revision
     "###);
@@ -391,7 +391,7 @@ fn test_new_insert_before_root() {
     "###);
 
     let stderr =
-        test_env.jj_cmd_failure(&repo_path, &["new", "--insert-before", "-m", "G", "root"]);
+        test_env.jj_cmd_failure(&repo_path, &["new", "--insert-before", "-m", "G", "root()"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot insert a commit before the root commit
     "###);
@@ -404,9 +404,9 @@ fn setup_before_insertion(test_env: &TestEnvironment, repo_path: &Path) {
     test_env.jj_cmd_success(repo_path, &["commit", "-m", "B"]);
     test_env.jj_cmd_success(repo_path, &["branch", "create", "C"]);
     test_env.jj_cmd_success(repo_path, &["describe", "-m", "C"]);
-    test_env.jj_cmd_success(repo_path, &["new", "-m", "D", "root"]);
+    test_env.jj_cmd_success(repo_path, &["new", "-m", "D", "root()"]);
     test_env.jj_cmd_success(repo_path, &["branch", "create", "D"]);
-    test_env.jj_cmd_success(repo_path, &["new", "-m", "E", "root"]);
+    test_env.jj_cmd_success(repo_path, &["new", "-m", "E", "root()"]);
     test_env.jj_cmd_success(repo_path, &["branch", "create", "E"]);
     test_env.jj_cmd_success(repo_path, &["new", "-m", "F", "D", "E"]);
     test_env.jj_cmd_success(repo_path, &["branch", "create", "F"]);

cli/tests/test_obslog_command.rs

@@ -26,7 +26,7 @@ fn test_obslog_with_or_without_diff() {
     test_env.jj_cmd_success(&repo_path, &["new", "-m", "my description"]);
     std::fs::write(repo_path.join("file1"), "foo\nbar\n").unwrap();
     std::fs::write(repo_path.join("file2"), "foo\n").unwrap();
-    test_env.jj_cmd_success(&repo_path, &["rebase", "-r", "@", "-d", "root"]);
+    test_env.jj_cmd_success(&repo_path, &["rebase", "-r", "@", "-d", "root()"]);
     std::fs::write(repo_path.join("file1"), "resolved\n").unwrap();
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["obslog"]);

cli/tests/test_rebase_command.rs

@@ -20,7 +20,7 @@ pub mod common;
 
 fn create_commit(test_env: &TestEnvironment, repo_path: &Path, name: &str, parents: &[&str]) {
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", name]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);
@@ -275,7 +275,7 @@ fn test_rebase_single_revision() {
 
     // Now, let's try moving the merge commit. After, both parents of "c" ("a" and
     // "b") should become parents of "d".
-    let stdout = test_env.jj_cmd_success(&repo_path, &["rebase", "-r", "c", "-d", "root"]);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["rebase", "-r", "c", "-d", "root()"]);
     insta::assert_snapshot!(stdout, @r###"
     Also rebased 1 descendant commits onto parent of rebased commit
     Working copy now at: vruxwmqv bf87078f d | d
@@ -401,8 +401,10 @@ fn test_rebase_multiple_destinations() {
     Error: More than one revset resolved to revision d370aee184ba
     "###);
 
-    let stderr =
+    let stderr = test_env.jj_cmd_failure(
-        test_env.jj_cmd_failure(&repo_path, &["rebase", "-r", "a", "-d", "b", "-d", "root"]);
+        &repo_path,
+        &["rebase", "-r", "a", "-d", "b", "-d", "root()"],
+    );
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot merge with root revision
     "###);

cli/tests/test_resolve_command.rs

@@ -26,7 +26,7 @@ fn create_commit(
     files: &[(&str, &str)],
 ) {
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", name]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);

cli/tests/test_restore_command.rs

@@ -69,7 +69,7 @@ fn test_restore() {
     insta::assert_snapshot!(stdout, @"");
 
     // Cannot restore the root revision
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["restore", "-c=root"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["restore", "-c=root()"]);
     insta::assert_snapshot!(stderr, @r###"
     Error: Cannot rewrite the root commit
     "###);
@@ -255,7 +255,7 @@ fn create_commit(
     files: &[(&str, &str)],
 ) {
     if parents.is_empty() {
-        test_env.jj_cmd_success(repo_path, &["new", "root", "-m", name]);
+        test_env.jj_cmd_success(repo_path, &["new", "root()", "-m", name]);
     } else {
         let mut args = vec!["new", "-m", name];
         args.extend(parents);

cli/tests/test_revset_output.rs

@@ -151,12 +151,12 @@ fn test_bad_function_call() {
       = Invalid arguments to revset function "branches": Invalid string pattern kind "bad"
     "###);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root::whatever()"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root()::whatever()"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Failed to parse revset:  --> 1:7
+    Error: Failed to parse revset:  --> 1:9
       |
-    1 | root::whatever()
+    1 | root()::whatever()
-      |       ^------^
+      |         ^------^
       |
       = Revset function "whatever" doesn't exist
     "###);
@@ -254,7 +254,7 @@ fn test_alias() {
     test_env.add_config(
         r###"
     [revset-aliases]
-    'my-root' = 'root'
+    'my-root' = 'root()'
     'syntax-error' = 'whatever &'
     'recurse' = 'recurse1'
     'recurse1' = 'recurse2()'
@@ -266,20 +266,20 @@ fn test_alias() {
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "my-root"]);
     insta::assert_snapshot!(stdout, @r###"
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     let stdout = test_env.jj_cmd_success(&repo_path, &["log", "-r", "identity(my-root)"]);
     insta::assert_snapshot!(stdout, @r###"
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root & syntax-error"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root() & syntax-error"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Failed to parse revset:  --> 1:8
+    Error: Failed to parse revset:  --> 1:10
       |
-    1 | root & syntax-error
+    1 | root() & syntax-error
-      |        ^----------^
+      |          ^----------^
       |
       = Alias "syntax-error" cannot be expanded
      --> 1:11
@@ -316,12 +316,12 @@ fn test_alias() {
       = Invalid arguments to revset function "author": Expected function argument of string pattern
     "###);
 
-    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root & recurse"]);
+    let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root() & recurse"]);
     insta::assert_snapshot!(stderr, @r###"
-    Error: Failed to parse revset:  --> 1:8
+    Error: Failed to parse revset:  --> 1:10
       |
-    1 | root & recurse
+    1 | root() & recurse
-      |        ^-----^
+      |          ^-----^
       |
       = Alias "recurse" cannot be expanded
      --> 1:1
@@ -384,16 +384,16 @@ fn test_bad_alias_decl() {
     test_env.add_config(
         r#"
     [revset-aliases]
-    'my-root' = 'root'
+    'my-root' = 'root()'
-    '"bad"' = 'root'
+    '"bad"' = 'root()'
-    'badfn(a, a)' = 'root'
+    'badfn(a, a)' = 'root()'
     "#,
     );
 
     // Invalid declaration should be warned and ignored.
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["log", "-r", "my-root"]);
     insta::assert_snapshot!(stdout, @r###"
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
     insta::assert_snapshot!(stderr, @r###"
     Failed to load "revset-aliases."bad"":  --> 1:1

cli/tests/test_templater.rs

@@ -33,9 +33,9 @@ fn test_templater_branches() {
     // Created some branches on the remote
     test_env.jj_cmd_success(&origin_path, &["describe", "-m=description 1"]);
     test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch1"]);
-    test_env.jj_cmd_success(&origin_path, &["new", "root", "-m=description 2"]);
+    test_env.jj_cmd_success(&origin_path, &["new", "root()", "-m=description 2"]);
     test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch2"]);
-    test_env.jj_cmd_success(&origin_path, &["new", "root", "-m=description 3"]);
+    test_env.jj_cmd_success(&origin_path, &["new", "root()", "-m=description 3"]);
     test_env.jj_cmd_success(&origin_path, &["branch", "create", "branch3"]);
     test_env.jj_cmd_success(&origin_path, &["git", "export"]);
     test_env.jj_cmd_success(

cli/tests/test_tree_level_conflicts.rs

@@ -24,9 +24,9 @@ fn test_enable_tree_level_conflicts() {
 
     // Create a few commits before we enable tree-level conflicts
     let file_path = repo_path.join("file");
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=left"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=left"]);
     std::fs::write(&file_path, "left").unwrap();
-    test_env.jj_cmd_success(&repo_path, &["new", "root", "-m=right"]);
+    test_env.jj_cmd_success(&repo_path, &["new", "root()", "-m=right"]);
     std::fs::write(&file_path, "right").unwrap();
     test_env.jj_cmd_success(
         &repo_path,
@@ -48,7 +48,7 @@ fn test_enable_tree_level_conflicts() {
     │ │  right
     ◉ │  rlvkpnrz test.user@example.com 2001-02-03 04:05:09.000 +07:00 32003b88
     ├─╯  left
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
 
     // Enable tree-level conflicts
@@ -65,7 +65,7 @@ fn test_enable_tree_level_conflicts() {
     │ │  right
     ◉ │  rlvkpnrz test.user@example.com 2001-02-03 04:05:09.000 +07:00 32003b88
     ├─╯  left
-    ◉  zzzzzzzz root 00000000
+    ◉  zzzzzzzz root() 00000000
     "###);
     // ...but at least it has no diff
     let stdout = test_env.jj_cmd_success(&repo_path, &["diff"]);

docs/glossary.md

@@ -159,9 +159,9 @@ copy rewrites the working copy commit.
 The root commit is a virtual commit at the root of every repository. It has a
 commit ID consisting of all '0's (`00000000...`) and a change ID consisting of
 all 'z's (`zzzzzzzz...`). It can be referred to in [revsets](#revset) by the
-special name `root`. Note that our definition of "root commit" is different from
+function `root()`. Note that our definition of "root commit" is different from
 Git's; Git's "root commits" are the first commit(s) in the repository, i.e. the
-commits `jj log -r root+` will show.
+commits `jj log -r root()+` will show.
 
 ## Tree
 

docs/revsets.md

@@ -18,9 +18,6 @@ ID or a Git ref pointing to them).
 
 ## Symbols
 
-The symbol `root` refers to the virtual commit that is the oldest ancestor of
-all other commits.
-
 The `@` expression refers to the working copy commit in the current workspace.
 Use `<workspace name>@` to refer to the working-copy commit in another
 workspace. Use `<name>@<remote>` to refer to a remote-tracking branch.
@@ -41,11 +38,10 @@ Taking shell quoting into account, you may need to use something like
 
 Jujutsu attempts to resolve a symbol in the following order:
 
-1. `root`
+1. Tag name
-2. Tag name
+2. Branch name
-3. Branch name
+3. Git ref
-4. Git ref
+4. Commit ID or change ID
-5. Commit ID or change ID
 
 ## Operators
 
@@ -107,6 +103,7 @@ revsets (expressions) as arguments.
 * `git_head()`: The Git `HEAD` target as of the last import. Equivalent to
   `present(HEAD@git)`.
 * `visible_heads()`: All visible heads (same as `heads(all())`).
+* `root()`: The virtual commit that is the oldest ancestor of all other commits.
 * `heads(x)`: Commits in `x` that are not ancestors of other commits in `x`.
   Note that this is different from
   [Mercurial's](https://repo.mercurial-scm.org/hg/help/revsets) `heads(x)`
@@ -127,7 +124,7 @@ revsets (expressions) as arguments.
 * `committer(pattern)`: Commits with the given string in the committer's
   name or email.
 * `empty()`: Commits modifying no files. This also includes `merges()` without
-  user modifications and `root`.
+  user modifications and `root()`.
 * `file(pattern..)`: Commits modifying the paths specified by the `pattern..`.
   Paths are relative to the directory `jj` was invoked from. A directory name
   will match all files in that directory and its subdirectories. For example,
@@ -186,7 +183,7 @@ jj log -r :@
 Show the initial commits in the repo (the ones Git calls "root commits"):
 
 ```
-jj log -r root+
+jj log -r root()+
 ```
 
 Show some important commits (like `git --simplify-by-decoration`):

docs/tutorial.md

@@ -137,12 +137,12 @@ for context.  The `~` indicates that the commit has parents that are not
 included in the graph. We can use the `-r` flag to select a different set of
 revisions to list. The flag accepts a ["revset"](revsets.md), which is an
 expression in a simple language for specifying revisions. For example, `@`
-refers to the working-copy commit, `root` refers to the root commit,
+refers to the working-copy commit, `root()` refers to the root commit,
 `branches()` refers to all commits pointed to by branches. We can combine
 expressions with `|` for union, `&` for intersection and `~` for difference. For
 example:
 ```shell
-$ jj log -r '@ | root | branches()'
+$ jj log -r '@ | root() | branches()'
 @  mpqrykypylvy martinvonz@google.com 2023-02-12 15:00:22.000 -08:00 aef4df99ea11
 ╷  (empty) (no description set)
 ╷ ◉  kowxouwzwxmv octocat@nowhere.com 2014-06-10 15:22:26.000 -07:00 test b3cbd5bbd7e8
@@ -156,8 +156,8 @@ $ jj log -r '@ | root | branches()'
 ```
 
 The `000000000000` commit (change ID `zzzzzzzzzzzz`) is a virtual commit that's
-called the "root commit". It's the root commit of every repo. The `root` symbol
+called the "root commit". It's the root commit of every repo. The `root()`
-in the revset matches it.
+function in the revset matches it.
 
 There are also operators for getting the parents (`foo-`), children (`foo+`),
 ancestors (`:foo`), descendants (`foo:`), DAG range (`foo:bar`, like

lib/src/revset.rs

@@ -256,6 +256,7 @@ pub enum RevsetCommitRef {
         remote: String,
     },
     VisibleHeads,
+    Root,
     Branches(StringPattern),
     RemoteBranches {
         branch_pattern: StringPattern,
@@ -363,6 +364,10 @@ impl RevsetExpression {
         Rc::new(RevsetExpression::CommitRef(RevsetCommitRef::VisibleHeads))
     }
 
+    pub fn root() -> Rc<RevsetExpression> {
+        Rc::new(RevsetExpression::CommitRef(RevsetCommitRef::Root))
+    }
+
     pub fn branches(pattern: StringPattern) -> Rc<RevsetExpression> {
         Rc::new(RevsetExpression::CommitRef(RevsetCommitRef::Branches(
             pattern,
@@ -1078,6 +1083,10 @@ static BUILTIN_FUNCTION_MAP: Lazy<HashMap<&'static str, RevsetFunction>> = Lazy:
         expect_no_arguments(name, arguments_pair)?;
         Ok(RevsetExpression::visible_heads())
     });
+    map.insert("root", |name, arguments_pair, _state| {
+        expect_no_arguments(name, arguments_pair)?;
+        Ok(RevsetExpression::root())
+    });
     map.insert("branches", |name, arguments_pair, state| {
         let ([], [opt_arg]) = expect_arguments(name, arguments_pair)?;
         let pattern = if let Some(arg) = opt_arg {
@@ -1966,8 +1975,8 @@ impl SymbolResolver for FailingSymbolResolver {
 
 pub type PrefixResolver<'a, T> = Box<dyn Fn(&dyn Repo, &HexPrefix) -> PrefixResolution<T> + 'a>;
 
-/// Resolves the "root" symbol, branches, remote branches, tags, git
+/// Resolves branches, remote branches, tags, git refs, and full and abbreviated
-/// refs, and full and abbreviated commit and change ids.
+/// commit and change ids.
 pub struct DefaultSymbolResolver<'a> {
     repo: &'a dyn Repo,
     commit_id_resolver: PrefixResolver<'a, CommitId>,
@@ -2002,68 +2011,66 @@ impl<'a> DefaultSymbolResolver<'a> {
 
 impl SymbolResolver for DefaultSymbolResolver<'_> {
     fn resolve_symbol(&self, symbol: &str) -> Result<Vec<CommitId>, RevsetResolutionError> {
-        if symbol == "root" {
+        if symbol.is_empty() {
-            Ok(vec![self.repo.store().root_commit_id().clone()])
+            return Err(RevsetResolutionError::EmptyString);
-        } else if symbol.is_empty() {
-            Err(RevsetResolutionError::EmptyString)
-        } else {
-            // Try to resolve as a tag
-            let target = self.repo.view().get_tag(symbol);
-            if target.is_present() {
-                return Ok(target.added_ids().cloned().collect());
-            }
-
-            // Try to resolve as a branch
-            if let Some(ids) = resolve_local_branch(self.repo, symbol) {
-                return Ok(ids);
-            }
-
-            // Try to resolve as a git ref
-            if let Some(ids) = resolve_git_ref(self.repo, symbol) {
-                return Ok(ids);
-            }
-
-            // Try to resolve as a full commit id.
-            if let Some(ids) = resolve_full_commit_id(self.repo, symbol)? {
-                return Ok(ids);
-            }
-
-            // Try to resolve as a commit id.
-            if let Some(prefix) = HexPrefix::new(symbol) {
-                match (self.commit_id_resolver)(self.repo, &prefix) {
-                    PrefixResolution::AmbiguousMatch => {
-                        return Err(RevsetResolutionError::AmbiguousCommitIdPrefix(
-                            symbol.to_owned(),
-                        ));
-                    }
-                    PrefixResolution::SingleMatch(id) => {
-                        return Ok(vec![id]);
-                    }
-                    PrefixResolution::NoMatch => {
-                        // Fall through
-                    }
-                }
-            }
-
-            // Try to resolve as a change id.
-            if let Some(prefix) = to_forward_hex(symbol).as_deref().and_then(HexPrefix::new) {
-                match (self.change_id_resolver)(self.repo, &prefix) {
-                    PrefixResolution::AmbiguousMatch => {
-                        return Err(RevsetResolutionError::AmbiguousChangeIdPrefix(
-                            symbol.to_owned(),
-                        ));
-                    }
-                    PrefixResolution::SingleMatch(ids) => {
-                        return Ok(ids);
-                    }
-                    PrefixResolution::NoMatch => {
-                        // Fall through
-                    }
-                }
-            }
-
-            Err(make_no_such_symbol_error(self.repo, symbol))
         }
+
+        // Try to resolve as a tag
+        let target = self.repo.view().get_tag(symbol);
+        if target.is_present() {
+            return Ok(target.added_ids().cloned().collect());
+        }
+
+        // Try to resolve as a branch
+        if let Some(ids) = resolve_local_branch(self.repo, symbol) {
+            return Ok(ids);
+        }
+
+        // Try to resolve as a git ref
+        if let Some(ids) = resolve_git_ref(self.repo, symbol) {
+            return Ok(ids);
+        }
+
+        // Try to resolve as a full commit id.
+        if let Some(ids) = resolve_full_commit_id(self.repo, symbol)? {
+            return Ok(ids);
+        }
+
+        // Try to resolve as a commit id.
+        if let Some(prefix) = HexPrefix::new(symbol) {
+            match (self.commit_id_resolver)(self.repo, &prefix) {
+                PrefixResolution::AmbiguousMatch => {
+                    return Err(RevsetResolutionError::AmbiguousCommitIdPrefix(
+                        symbol.to_owned(),
+                    ));
+                }
+                PrefixResolution::SingleMatch(id) => {
+                    return Ok(vec![id]);
+                }
+                PrefixResolution::NoMatch => {
+                    // Fall through
+                }
+            }
+        }
+
+        // Try to resolve as a change id.
+        if let Some(prefix) = to_forward_hex(symbol).as_deref().and_then(HexPrefix::new) {
+            match (self.change_id_resolver)(self.repo, &prefix) {
+                PrefixResolution::AmbiguousMatch => {
+                    return Err(RevsetResolutionError::AmbiguousChangeIdPrefix(
+                        symbol.to_owned(),
+                    ));
+                }
+                PrefixResolution::SingleMatch(ids) => {
+                    return Ok(ids);
+                }
+                PrefixResolution::NoMatch => {
+                    // Fall through
+                }
+            }
+        }
+
+        Err(make_no_such_symbol_error(self.repo, symbol))
     }
 }
 
@@ -2086,6 +2093,7 @@ fn resolve_commit_ref(
             }
         }
         RevsetCommitRef::VisibleHeads => Ok(repo.view().heads().iter().cloned().collect_vec()),
+        RevsetCommitRef::Root => Ok(vec![repo.store().root_commit_id().clone()]),
         RevsetCommitRef::Branches(pattern) => {
             let view = repo.view();
             let commit_ids = filter_map_values_by_key_pattern(view.branches(), pattern)
@@ -2995,6 +3003,11 @@ mod tests {
                 message: "Expected 1 arguments".to_string()
             })
         );
+        assert_eq!(
+            parse("root()"),
+            Ok(Rc::new(RevsetExpression::CommitRef(RevsetCommitRef::Root)))
+        );
+        assert!(parse("root(a)").is_err());
         assert_eq!(
             parse(r#"description("")"#),
             Ok(RevsetExpression::filter(

lib/tests/test_revset.rs

@@ -70,18 +70,6 @@ fn revset_for_commits<'index>(
         .unwrap()
 }
 
-#[test_case(false ; "local backend")]
-#[test_case(true ; "git backend")]
-fn test_resolve_symbol_root(use_git: bool) {
-    let test_repo = TestRepo::init(use_git);
-    let repo = &test_repo.repo;
-
-    assert_matches!(
-        resolve_symbol(repo.as_ref(), "root"),
-        Ok(v) if v == vec![repo.store().root_commit_id().clone()]
-    );
-}
-
 #[test]
 fn test_resolve_symbol_empty_string() {
     let test_repo = TestRepo::init(true);
@@ -738,16 +726,20 @@ fn test_resolve_symbol_git_refs() {
         vec![commit2.id().clone()]
     );
 
-    // Cannot shadow root symbols
+    // "@" (quoted) can be resolved, and root is a normal symbol.
     let ws_id = WorkspaceId::default();
     mut_repo
         .set_wc_commit(ws_id.clone(), commit1.id().clone())
         .unwrap();
     mut_repo.set_git_ref_target("@", RefTarget::normal(commit2.id().clone()));
     mut_repo.set_git_ref_target("root", RefTarget::normal(commit3.id().clone()));
+    assert_eq!(
+        resolve_symbol(mut_repo, r#""@""#).unwrap(),
+        vec![commit2.id().clone()]
+    );
     assert_eq!(
         resolve_symbol(mut_repo, "root").unwrap(),
-        vec![mut_repo.store().root_commit().id().clone()]
+        vec![commit3.id().clone()]
     );
 
     // Conflicted ref resolves to its "adds"
@@ -812,7 +804,7 @@ fn test_evaluate_expression_root_and_checkout(use_git: bool) {
 
     // Can find the root commit
     assert_eq!(
-        resolve_commit_ids(mut_repo, "root"),
+        resolve_commit_ids(mut_repo, "root()"),
         vec![root_commit.id().clone()]
     );
 
@@ -847,7 +839,7 @@ fn test_evaluate_expression_heads(use_git: bool) {
 
     // Heads of the root is the root
     assert_eq!(
-        resolve_commit_ids(mut_repo, "heads(root)"),
+        resolve_commit_ids(mut_repo, "heads(root())"),
         vec![root_commit.id().clone()]
     );
 
@@ -912,7 +904,7 @@ fn test_evaluate_expression_roots(use_git: bool) {
 
     // Roots of the root is the root
     assert_eq!(
-        resolve_commit_ids(mut_repo, "roots(root)"),
+        resolve_commit_ids(mut_repo, "roots(root())"),
         vec![root_commit.id().clone()]
     );
 
@@ -966,7 +958,7 @@ fn test_evaluate_expression_parents(use_git: bool) {
     let commit5 = graph_builder.commit_with_parents(&[&commit2]);
 
     // The root commit has no parents
-    assert_eq!(resolve_commit_ids(mut_repo, "root-"), vec![]);
+    assert_eq!(resolve_commit_ids(mut_repo, "root()-"), vec![]);
 
     // Can find parents of the current working-copy commit
     mut_repo
@@ -1065,7 +1057,7 @@ fn test_evaluate_expression_children(use_git: bool) {
 
     // Can find children of the root commit
     assert_eq!(
-        resolve_commit_ids(mut_repo, "root+"),
+        resolve_commit_ids(mut_repo, "root()+"),
         vec![commit1.id().clone()]
     );
 
@@ -1094,11 +1086,11 @@ fn test_evaluate_expression_children(use_git: bool) {
 
     // Can find children of children, which may be optimized to single query
     assert_eq!(
-        resolve_commit_ids(mut_repo, "root++"),
+        resolve_commit_ids(mut_repo, "root()++"),
         vec![commit4.id().clone(), commit2.id().clone()]
     );
     assert_eq!(
-        resolve_commit_ids(mut_repo, &format!("(root | {})++", commit1.id().hex())),
+        resolve_commit_ids(mut_repo, &format!("(root() | {})++", commit1.id().hex())),
         vec![
             commit5.id().clone(),
             commit4.id().clone(),
@@ -1136,7 +1128,7 @@ fn test_evaluate_expression_ancestors(use_git: bool) {
 
     // The ancestors of the root commit is just the root commit itself
     assert_eq!(
-        resolve_commit_ids(mut_repo, ":root"),
+        resolve_commit_ids(mut_repo, ":root()"),
         vec![root_commit.id().clone()]
     );
 
@@ -1205,7 +1197,7 @@ fn test_evaluate_expression_range(use_git: bool) {
 
     // The range from the root to the root is empty (because the left side of the
     // range is exclusive)
-    assert_eq!(resolve_commit_ids(mut_repo, "root..root"), vec![]);
+    assert_eq!(resolve_commit_ids(mut_repo, "root()..root()"), vec![]);
 
     // Linear range
     assert_eq!(
@@ -1267,7 +1259,7 @@ fn test_evaluate_expression_dag_range(use_git: bool) {
 
     // Can get DAG range of just the root commit
     assert_eq!(
-        resolve_commit_ids(mut_repo, "root:root"),
+        resolve_commit_ids(mut_repo, "root():root()"),
         vec![root_commit_id.clone()]
     );
 
@@ -1364,7 +1356,7 @@ fn test_evaluate_expression_connected(use_git: bool) {
 
     // Can connect just the root commit
     assert_eq!(
-        resolve_commit_ids(mut_repo, "connected(root)"),
+        resolve_commit_ids(mut_repo, "connected(root())"),
         vec![root_commit_id.clone()]
     );
 
@@ -1454,7 +1446,7 @@ fn test_evaluate_expression_descendants(use_git: bool) {
 
     // The descendants of the root commit are all the commits in the repo
     assert_eq!(
-        resolve_commit_ids(mut_repo, "root:"),
+        resolve_commit_ids(mut_repo, "root():"),
         vec![
             commit6.id().clone(),
             commit5.id().clone(),
@@ -1939,7 +1931,7 @@ fn test_evaluate_expression_latest(use_git: bool) {
 
     // Should not panic if count is larger than the candidates size
     assert_eq!(
-        resolve_commit_ids(mut_repo, "latest(~root, 5)"),
+        resolve_commit_ids(mut_repo, "latest(~root(), 5)"),
         vec![
             commit4_t1.id().clone(),
             commit3_t2.id().clone(),
@@ -2091,7 +2083,7 @@ fn test_evaluate_expression_author(use_git: bool) {
     assert_eq!(
         resolve_commit_ids(
             mut_repo,
-            &format!("root.. & (author(name1) | {})", commit3.id().hex())
+            &format!("root().. & (author(name1) | {})", commit3.id().hex())
         ),
         vec![commit3.id().clone(), commit1.id().clone()]
     );
@@ -2156,7 +2148,7 @@ fn test_evaluate_expression_mine(use_git: bool) {
     assert_eq!(
         resolve_commit_ids(
             mut_repo,
-            &format!("root.. & (mine() | {})", commit1.id().hex())
+            &format!("root().. & (mine() | {})", commit1.id().hex())
         ),
         vec![
             commit3.id().clone(),
@@ -2481,7 +2473,7 @@ fn test_evaluate_expression_filter_combinator(use_git: bool) {
 
     // Intersected with a set node
     assert_eq!(
-        resolve_commit_ids(mut_repo, "root.. & ~description(1)"),
+        resolve_commit_ids(mut_repo, "root().. & ~description(1)"),
         vec![commit3.id().clone(), commit2.id().clone()],
     );
     assert_eq!(