cli: make jj show accept a template

CHANGELOG.md

@@ -17,6 +17,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Templates now support logical operators: `||`, `&&`, `!`
 
+* `jj show` now accepts `-T`/`--template` option to render a description using
+  template
+
 ### Fixed bugs
 
 * On Windows, symlinks in the repo are now materialized as regular files in the

cli/src/commands/show.rs

@@ -28,6 +28,11 @@ pub(crate) struct ShowArgs {
     /// Ignored (but lets you pass `-r` for consistency with other commands)
     #[arg(short = 'r', hide = true)]
     unused_revision: bool,
+    /// Render description of a revision using the given template
+    ///
+    /// For the syntax, see https://github.com/martinvonz/jj/blob/main/docs/templates.md
+    #[arg(long, short = 'T')]
+    template: Option<String>,
     #[command(flatten)]
     format: DiffFormatArgs,
 }
@@ -40,7 +45,10 @@ pub(crate) fn cmd_show(
 ) -> Result<(), CommandError> {
     let workspace_command = command.workspace_helper(ui)?;
     let commit = workspace_command.resolve_single_rev(&args.revision, ui)?;
-    let template_string = command.settings().config().get_string("templates.show")?;
+    let template_string = match &args.template {
+        Some(value) => value.to_string(),
+        None => command.settings().config().get_string("templates.show")?,
+    };
     let template = workspace_command.parse_commit_template(&template_string)?;
     let diff_formats = diff_util::diff_formats_for(command.settings(), &args.format)?;
     ui.request_pager();

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

@@ -1551,6 +1551,7 @@ Show commit description and changes in a revision
 
   Possible values: `true`, `false`
 
+* `-T`, `--template <TEMPLATE>` — Render description of a revision using the given template
 * `-s`, `--summary` — For each path, show only whether it was modified, added, or deleted
 
   Possible values: `true`, `false`

cli/tests/test_show_command.rs

@@ -34,6 +34,20 @@ fn test_show() {
     "###);
 }
 
+#[test]
+fn test_show_with_template() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+    test_env.jj_cmd_ok(&repo_path, &["new", "-m", "a new commit"]);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["show", "-T", "description"]);
+
+    insta::assert_snapshot!(stdout, @r###"
+    a new commit
+    "###);
+}
+
 #[test]
 fn test_show_relative_timestamps() {
     let test_env = TestEnvironment::default();