cli_util: Move flags if help command is used

The default clap's help command doesn't have the ability to accept flags
(e.g --no-pager). So move them if the help command is used.

Fixes: #4501

cli/src/cli_util.rs

@@ -3007,6 +3007,46 @@ fn resolve_aliases(
     }
 }
 
+fn move_global_args_if_help_cmd(
+    app: &Command,
+    args: Vec<String>,
+) -> Result<Vec<String>, CommandError> {
+    let has_help_cmd = args[..args.len() - 1].iter().any(|str| str == "help");
+
+    if !has_help_cmd {
+        return Ok(args);
+    }
+
+    let args_without_help = args.iter().filter(|&str| str != "help");
+
+    let mut curr_matches = &app
+        .clone()
+        .allow_external_subcommands(true)
+        .ignore_errors(true)
+        .try_get_matches_from(args_without_help)?;
+
+    let mut cmds = vec!["help"];
+
+    while let Some((subcmd_name, matches)) = curr_matches.subcommand() {
+        cmds.push(subcmd_name);
+
+        curr_matches = matches;
+    }
+
+    let (ret, rest) = args.split_at(1);
+    let mut ret = ret.to_vec();
+
+    let (commands, args): (Vec<_>, Vec<_>) = rest
+        .iter()
+        .cloned()
+        .partition(|str| cmds.contains(&str.as_str()));
+
+    ret.extend(args);
+    ret.extend(commands);
+
+    Ok(ret)
+}
+
 /// Parse args that must be interpreted early, e.g. before printing help.
 fn handle_early_args(
     ui: &mut Ui,
@@ -3055,8 +3095,9 @@ pub fn expand_args(
         }
     }
 
-    let string_args = resolve_default_command(ui, config, app, string_args)?;
-    resolve_aliases(ui, config, app, string_args)
+    let mut string_args = resolve_default_command(ui, config, app, string_args)?;
+    string_args = resolve_aliases(ui, config, app, string_args)?;
+    move_global_args_if_help_cmd(app, string_args)
 }
 
 pub fn parse_args(

cli/tests/runner.rs

@@ -44,6 +44,7 @@ mod test_git_remotes;
 mod test_git_submodule;
 mod test_gitignores;
 mod test_global_opts;
+mod test_help_command;
 mod test_immutable_commits;
 mod test_init_command;
 mod test_interdiff_command;

cli/tests/test_global_opts.rs

@@ -530,6 +530,10 @@ fn test_early_args() {
     let stdout = test_env.jj_cmd_success(test_env.env_root(), &["--color=always", "help"]);
     insta::assert_snapshot!(stdout.lines().find(|l| l.contains("Commands:")).unwrap(), @"Commands:");
 
+    // Check that early args are accepted after the help command
+    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["help", "--color=always"]);
+    insta::assert_snapshot!(stdout.lines().find(|l| l.contains("Commands:")).unwrap(), @"Commands:");
+
     // Early args are parsed with clap's ignore_errors(), but there is a known
     // bug that causes defaults to be unpopulated. Test that the early args are
     // tolerant of this bug and don't cause a crash.

cli/tests/test_help_command.rs

@@ -0,0 +1,46 @@
+// Copyright 2024 The Jujutsu Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use crate::common::TestEnvironment;
+
+#[test]
+fn test_help() {
+    let test_env = TestEnvironment::default();
+
+    let help_cmd_stdout = test_env.jj_cmd_success(test_env.env_root(), &["help"]);
+    // The help command output should be equal to the long --help flag
+    let help_flag_stdout = test_env.jj_cmd_success(test_env.env_root(), &["--help"]);
+    assert_eq!(help_cmd_stdout, help_flag_stdout);
+
+    // Help command should work with commands
+    let help_cmd_stdout = test_env.jj_cmd_success(test_env.env_root(), &["help", "log"]);
+    let help_flag_stdout = test_env.jj_cmd_success(test_env.env_root(), &["log", "--help"]);
+    assert_eq!(help_cmd_stdout, help_flag_stdout);
+
+    // Help command should work with subcommands
+    let help_cmd_stdout =
+        test_env.jj_cmd_success(test_env.env_root(), &["help", "workspace", "add"]);
+    let help_flag_stdout =
+        test_env.jj_cmd_success(test_env.env_root(), &["workspace", "add", "--help"]);
+    assert_eq!(help_cmd_stdout, help_flag_stdout);
+
+    // Help command should work recursively
+    let help_cmd_stdout =
+        test_env.jj_cmd_success(test_env.env_root(), &["workspace", "help", "add"]);
+    let help_flag_stdout =
+        test_env.jj_cmd_success(test_env.env_root(), &["workspace", "add", "--help"]);
+    assert_eq!(help_cmd_stdout, help_flag_stdout);
+
+    let _ = test_env.jj_cmd_failure(test_env.env_root(), &["workspace", "add", "help"]);
+}