cli: use a positional argument for jj util completion

this has two main advantages:
- it makes it clear that the shells are mutually exclusive
- it allows us to extend the command with shell-specific options in the future if necessary
as a happy accident, it also adds support for `elvish` and `powershell`.

for backwards compatibility, this also keeps the existing options as hidden flags.

i am not super happy with how the new help looks; the instructions for setting up the shell are
squished together and IMO a little harder to read. i'm open to suggestions.

CHANGELOG.md

@@ -39,8 +39,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   of `R` for "Removed". @joyously pointed out that `R` could also mean
   "Renamed".
 
+* `jj util completion` now takes the shell as a positional argument, not a flag.
+  the previous behavior is deprecated, but supported for now. it will be removed
+  in the future.
+
 ### New features
 
+* `jj util completion` now supports powershell and elvish.
+
 * Official binaries for macOS running on Apple Silicon (`aarch64-apple-darwin`)
   are now available, alongside the existing macOS x86 binaries.
 

cli/src/commands/util.rs

@@ -17,6 +17,7 @@ use std::slice;
 use std::time::{Duration, SystemTime};
 
 use clap::Subcommand;
+use clap_complete::Shell;
 use jj_lib::repo::Repo;
 use tracing::instrument;
 
@@ -34,30 +35,26 @@ pub(crate) enum UtilCommand {
 }
 
 /// Print a command-line-completion script
+///
+/// Apply it by running this:
+/// bash: source <(jj util completion)
+/// fish: jj util completion --fish | source
+/// zsh:
+/// autoload -U compinit
+/// compinit
+/// source <(jj util completion --zsh)
 #[derive(clap::Args, Clone, Debug)]
+#[command(verbatim_doc_comment)]
 pub(crate) struct UtilCompletionArgs {
-    /// Print a completion script for Bash (default)
-    ///
-    /// Apply it by running this:
-    ///
-    /// source <(jj util completion)
-    #[arg(long, verbatim_doc_comment)]
+    shell: Option<Shell>,
+    /// Deprecated. Use the SHELL positional argument instead.
+    #[arg(long, hide = true)]
     bash: bool,
-    /// Print a completion script for Fish
-    ///
-    /// Apply it by running this:
-    ///
-    /// jj util completion --fish | source
-    #[arg(long, verbatim_doc_comment)]
+    /// Deprecated. Use the SHELL positional argument instead.
+    #[arg(long, hide = true)]
     fish: bool,
-    /// Print a completion script for Zsh
-    ///
-    /// Apply it by running this:
-    ///
-    /// autoload -U compinit
-    /// compinit
-    /// source <(jj util completion --zsh)
-    #[arg(long, verbatim_doc_comment)]
+    /// Deprecated. Use the SHELL positional argument instead.
+    #[arg(long, hide = true)]
     zsh: bool,
 }
 
@@ -109,13 +106,35 @@ fn cmd_util_completion(
     args: &UtilCompletionArgs,
 ) -> Result<(), CommandError> {
     let mut app = command.app().clone();
+    let warn = |shell| {
+        writeln!(
+            ui.warning(),
+            "warning: `jj util completion --{shell}` will be removed in a future version, and \
+             this will be a hard error"
+        )
+    };
     let mut buf = vec![];
-    let shell = if args.zsh {
-        clap_complete::Shell::Zsh
-    } else if args.fish {
-        clap_complete::Shell::Fish
-    } else {
-        clap_complete::Shell::Bash
+    let shell = match (args.shell, args.fish, args.zsh, args.bash) {
+        (Some(s), false, false, false) => s,
+        // allow `--fish` and `--zsh` for back-compat, but don't allow them to be combined
+        (None, true, false, false) => {
+            warn("fish")?;
+            Shell::Fish
+        }
+        (None, false, true, false) => {
+            warn("zsh")?;
+            Shell::Zsh
+        }
+        // default to bash for back-compat. TODO: consider making `shell` a required argument
+        (None, false, false, _) => {
+            warn("bash")?;
+            Shell::Bash
+        }
+        _ => {
+            return Err(user_error(
+                "cannot generate completion for multiple shells at once",
+            ))
+        }
     };
     clap_complete::generate(shell, &mut app, "jj", &mut buf);
     ui.stdout_formatter().write_all(&buf)?;

cli/tests/cli-reference@.md.snap

@@ -1708,19 +1708,34 @@ Infrequently used commands such as for generating shell completions
 
 Print a command-line-completion script
 
-**Usage:** `jj util completion [OPTIONS]`
+Apply it by running this:
+bash: source <(jj util completion)
+fish: jj util completion --fish | source
+zsh:
+autoload -U compinit
+compinit
+source <(jj util completion --zsh)
+
+**Usage:** `jj util completion [SHELL]`
+
+###### **Arguments:**
+
+* `<SHELL>`
+
+  Possible values: `bash`, `elvish`, `fish`, `powershell`, `zsh`
+
 
 ###### **Options:**
 
-* `--bash` — Print a completion script for Bash (default)
+* `--bash` — Deprecated. Use the SHELL positional argument instead
 
   Possible values: `true`, `false`
 
-* `--fish` — Print a completion script for Fish
+* `--fish` — Deprecated. Use the SHELL positional argument instead
 
   Possible values: `true`, `false`
 
-* `--zsh` — Print a completion script for Zsh
+* `--zsh` — Deprecated. Use the SHELL positional argument instead
 
   Possible values: `true`, `false`
 

cli/tests/test_shell_completion.rs

@@ -0,0 +1,30 @@
+// 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;
+
+pub mod common;
+
+#[test]
+fn test_deprecated_flags() {
+    let test_env = TestEnvironment::default();
+    let (stdout, stderr) =
+        test_env.jj_cmd_ok(test_env.env_root(), &["util", "completion", "--bash"]);
+    assert_eq!(
+        stderr,
+        "warning: `jj util completion --bash` will be removed in a future version, and this will \
+         be a hard error\n"
+    );
+    assert!(stdout.contains("COMPREPLY"));
+}