cli: make jj merge delegate to jj new

CHANGELOG.md

@@ -30,6 +30,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj new` now always checks out the new commit (used to be only if the parent
   was `@`).
 
+* `jj merge` now checks out the new commit. The command now behaves exactly
+  like `jj new`, except that it requires at least two arguments.
+  
+
 * When the working-copy commit is abandoned by `jj abandon` and the parent
   commit is open, a new working-copy commit will be created on top (the open
   parent commit used to get checked out).
@@ -141,8 +145,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * `jj checkout` now lets you specify a description with `--message/-m`.
 
-* `jj merge` now outputs the id of the newly created commit.
-
 * `jj new` can now be used for creating merge commits. If you pass more than
   one argument to it, the new commit will have all of them as parents.
 

src/commands.rs

@@ -1114,7 +1114,16 @@ enum Commands {
     Restore(RestoreArgs),
     Touchup(TouchupArgs),
     Split(SplitArgs),
-    Merge(MergeArgs),
+    /// Merge work from multiple branches
+    ///
+    /// Unlike most other VCSs, `jj merge` does not implicitly include the
+    /// working copy revision's parent as one of the parents of the merge;
+    /// you need to explicitly list all revisions that should become parents
+    /// of the merge.
+    ///
+    /// This is the same as `jj new`, except that it requires at least two
+    /// arguments.
+    Merge(NewArgs),
     Rebase(RebaseArgs),
     Backout(BackoutArgs),
     #[clap(subcommand)]
@@ -1541,20 +1550,6 @@ struct SplitArgs {
     paths: Vec<String>,
 }
 
-/// Merge work from multiple branches
-///
-/// Unlike most other VCSs, `jj merge` does not implicitly include the working
-/// copy revision's parent as one of the parents of the merge; you need to
-/// explicitly list all revisions that should become parents of the merge. Also,
-/// you need to explicitly check out the resulting revision if you want to.
-#[derive(clap::Args, Clone, Debug)]
-struct MergeArgs {
-    revisions: Vec<String>,
-    /// The change description to use (don't open editor)
-    #[clap(long, short)]
-    message: Option<String>,
-}
-
 /// Move revisions to a different parent
 ///
 /// There are three different ways of specifying which revisions to rebase:
@@ -3956,50 +3951,13 @@ any changes, then the operation will be aborted.
     Ok(())
 }
 
-fn cmd_merge(ui: &mut Ui, command: &CommandHelper, args: &MergeArgs) -> Result<(), CommandError> {
+fn cmd_merge(ui: &mut Ui, command: &CommandHelper, args: &NewArgs) -> Result<(), CommandError> {
-    let mut workspace_command = command.workspace_helper(ui)?;
+    if args.revisions.len() < 2 {
-    let revision_args = &args.revisions;
+        return Err(CommandError::CliError(String::from(
-    if revision_args.len() < 2 {
-        return Err(CommandError::UserError(String::from(
             "Merge requires at least two revisions",
         )));
     }
-    let mut commits = vec![];
+    cmd_new(ui, command, args)
-    let mut parent_ids = vec![];
-    for revision_arg in revision_args {
-        // TODO: Should we allow each argument to resolve to multiple revisions?
-        // It would be neat to be able to do `jj merge main` when `main` is conflicted,
-        // but I'm not sure it would actually be useful.
-        let commit = workspace_command.resolve_single_rev(revision_arg)?;
-        parent_ids.push(commit.id().clone());
-        commits.push(commit);
-    }
-    let description = if let Some(message) = &args.message {
-        message.to_string()
-    } else {
-        edit_description(
-            ui,
-            workspace_command.repo(),
-            "\n\nJJ: Enter commit description for the merge commit.\n",
-        )?
-    };
-    let merged_tree = merge_commit_trees(workspace_command.repo().as_repo_ref(), &commits);
-    let mut tx = workspace_command.start_transaction("merge commits");
-    let new_commit = CommitBuilder::for_new_commit(ui.settings(), merged_tree.id().clone())
-        .set_parents(parent_ids)
-        .set_description(description)
-        .set_open(false)
-        .write_to_repo(tx.mut_repo());
-    ui.write("Created merge commit: ")?;
-    ui.write_commit_summary(
-        workspace_command.repo().as_repo_ref(),
-        &workspace_command.workspace_id(),
-        &new_commit,
-    )?;
-    ui.write("\n")?;
-    workspace_command.finish_transaction(ui, tx)?;
-
-    Ok(())
 }
 
 fn cmd_rebase(ui: &mut Ui, command: &CommandHelper, args: &RebaseArgs) -> Result<(), CommandError> {

tests/test_new_command.rs

@@ -70,6 +70,22 @@ fn test_new_merge() {
     insta::assert_snapshot!(stdout, @"a");
     let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file2"]);
     insta::assert_snapshot!(stdout, @"b");
+
+    // Same test with `jj merge`
+    test_env.jj_cmd_success(&repo_path, &["undo"]);
+    test_env.jj_cmd_success(&repo_path, &["merge", "main", "@"]);
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    @   c34d60aa33225c2080da52faa39980efe944bddd (no description set)
+    |\  
+    o | 99814c62bec5c13d2053435b3d6bbeb1900cb57e add file2
+    | o fe37af248a068697c6dcd7ebd17f5aac2205e7cb add file1
+    |/  
+    o 0000000000000000000000000000000000000000 (no description set)
+    "###);
+
+    // `jj merge` with less than two arguments is an error
+    test_env.jj_cmd_cli_error(&repo_path, &["merge"]);
+    test_env.jj_cmd_cli_error(&repo_path, &["merge", "main"]);
 }
 
 fn get_log_output(test_env: &TestEnvironment, repo_path: &Path) -> String {