cli: in help output, list global options under separate heading

I've found it hard to read the `jj help` output because command
options are mixed with global options. This patch fixes that by
putting global options under a separate heading.

src/commands.rs

@@ -868,7 +868,11 @@ fn update_working_copy(
 /// To get started, see the tutorial at https://github.com/martinvonz/jj/blob/main/docs/tutorial.md.
 #[derive(clap::Parser, Clone, Debug)]
 #[clap(author = "Martin von Zweigbergk <martinvonz@google.com>", version)]
-#[clap(mut_arg("help", |arg| { arg.help("Print help information, more help with --help than with -h")}))]
+#[clap(mut_arg("help", |arg| {
+    arg
+        .help("Print help information, more help with --help than with -h")
+        .help_heading("GLOBAL OPTIONS")
+    }))]
 struct Args {
     #[clap(subcommand)]
     command: Commands,
@@ -876,7 +880,7 @@ struct Args {
     ///
     /// By default, Jujutsu searches for the closest .jj/ directory in an
     /// ancestor of the current working directory.
-    #[clap(long, short = 'R', global = true)]
+    #[clap(long, short = 'R', global = true, help_heading = "GLOBAL OPTIONS")]
     repository: Option<String>,
     /// Don't commit the working copy
     ///
@@ -886,7 +890,7 @@ struct Args {
     /// stale working copy commit, you can use `--no-commit-working-copy`.
     /// This may be useful e.g. in a command prompt, especially if you have
     /// another process that commits the working copy.
-    #[clap(long, global = true)]
+    #[clap(long, global = true, help_heading = "GLOBAL OPTIONS")]
     no_commit_working_copy: bool,
     /// Operation to load the repo at
     ///
@@ -907,7 +911,13 @@ struct Args {
     /// operation. Doing that is equivalent to having run concurrent commands
     /// starting at the earlier operation. There's rarely a reason to do that,
     /// but it is possible.
-    #[clap(long, alias = "at-op", global = true, default_value = "@")]
+    #[clap(
+        long,
+        alias = "at-op",
+        global = true,
+        help_heading = "GLOBAL OPTIONS",
+        default_value = "@"
+    )]
     at_operation: String,
 }
 

tests/test_global_opts.rs

@@ -104,3 +104,27 @@ fn test_invalid_config() {
     insta::assert_snapshot!(stdout, @"Invalid config: expected newline, found an identifier at line 1 column 10 in config.toml
 ");
 }
+
+#[test]
+fn test_help() {
+    // Test that global options are separated out in the help output
+    let test_env = TestEnvironment::default();
+
+    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["edit", "-h"]);
+    insta::assert_snapshot!(stdout.replace(".exe", ""), @r###"
+    jj-edit 
+    Edit the content changes in a revision
+
+    USAGE:
+        jj edit [OPTIONS]
+
+    OPTIONS:
+        -r, --revision <REVISION>    The revision to edit [default: @]
+
+    GLOBAL OPTIONS:
+            --at-operation <AT_OPERATION>    Operation to load the repo at [default: @]
+        -h, --help                           Print help information, more help with --help than with -h
+            --no-commit-working-copy         Don't commit the working copy
+        -R, --repository <REPOSITORY>        Path to repository to operate on
+    "###);
+}