jj new --insert

src/commands/mod.rs

@@ -438,6 +438,7 @@ struct EditArgs {
 /// For more information, see
 /// https://github.com/martinvonz/jj/blob/main/docs/working-copy.md.
 #[derive(clap::Args, Clone, Debug)]
+#[command(group(ArgGroup::new("order").args(&["rebase_children", "insert"])))]
 struct NewArgs {
     /// Parent(s) of the new change
     #[arg(default_value = "@")]
@@ -451,6 +452,9 @@ struct NewArgs {
     /// Rebase the children of the parents onto the new change
     #[arg(long, short = 'C')]
     rebase_children: bool,
+    /// Insert the commit before the given changes
+    #[arg(long, short = 'I')]
+    insert: bool,
 }
 
 /// Move changes from one revision into another
@@ -1979,7 +1983,7 @@ fn cmd_new(ui: &mut Ui, command: &CommandHelper, args: &NewArgs) -> Result<(), C
     let parent_ids = commits.iter().map(|c| c.id().clone()).collect::<Vec<_>>();
     let mut tx = workspace_command.start_transaction("new empty commit");
     let merged_tree = merge_commit_trees(tx.base_repo().as_repo_ref(), &commits);
-    let new_commit = tx
+    let mut new_commit = tx
         .mut_repo()
         .new_commit(
             command.settings(),
@@ -1990,6 +1994,7 @@ fn cmd_new(ui: &mut Ui, command: &CommandHelper, args: &NewArgs) -> Result<(), C
         .write()?;
     let mut num_rebased = 0;
     if args.rebase_children {
+        // Replace parents in all children by the new commit
         let parents = RevsetExpression::commits(parent_ids);
         let children = tx
             .base_workspace_helper()
@@ -2019,6 +2024,34 @@ fn cmd_new(ui: &mut Ui, command: &CommandHelper, args: &NewArgs) -> Result<(), C
                 &new_parents,
             )?;
         }
+    } else if args.insert {
+        // Instead of having the new commit as a child of the
+        // changes given on the command line, add it between
+        // the changes parents and the changes.
+        let parents = RevsetExpression::commits(parent_ids.clone());
+        let parents_parents = tx
+            .base_workspace_helper()
+            .evaluate_revset(&parents.parents())?
+            .iter()
+            .map(|c| c.commit_id())
+            .collect::<Vec<_>>();
+        new_commit = tx
+            .mut_repo()
+            .rewrite_commit(command.settings(), &new_commit)
+            .set_parents(parents_parents)
+            .write()?;
+        num_rebased = parent_ids.len();
+        for parent_id in parent_ids {
+            let parent_commit = tx
+                .base_workspace_helper()
+                .resolve_single_rev(&parent_id.hex())?;
+            rebase_commit(
+                command.settings(),
+                tx.mut_repo(),
+                &parent_commit,
+                &[new_commit.clone()],
+            )?;
+        }
     }
     if num_rebased > 0 {
         writeln!(ui, "Rebased {num_rebased} descendant commits")?;

tests/test_new_command.rs

@@ -151,6 +151,46 @@ fn test_new_rebase_children() {
     "###);
 }
 
+#[test]
+fn test_new_insert() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
+    setup_before_insertion(&test_env, &repo_path);
+    insta::assert_snapshot!(get_short_log_output(&test_env, &repo_path), @r###"
+    @   F
+    |\  
+    o | E
+    | o D
+    |/  
+    | o C
+    | o B
+    | o A
+    |/  
+    o root
+    "###);
+
+    let stdout = test_env.jj_cmd_success(&repo_path, &["new", "--insert", "-m", "G", "C", "F"]);
+    insta::assert_snapshot!(stdout, @r###"
+    Rebased 2 descendant commits
+    Working copy now at: ff6bbbc7b8df G
+    "###);
+    insta::assert_snapshot!(get_short_log_output(&test_env, &repo_path), @r###"
+    o F
+    | o C
+    |/  
+    @-.   G
+    |\ \  
+    o | | E
+    | o | D
+    |/ /  
+    | o B
+    | o A
+    |/  
+    o root
+    "###);
+}
+
 fn setup_before_insertion(test_env: &TestEnvironment, repo_path: &Path) {
     test_env.jj_cmd_success(repo_path, &["branch", "create", "A"]);
     test_env.jj_cmd_success(repo_path, &["commit", "-m", "A"]);