diff --git a/cli/src/commands/mod.rs b/cli/src/commands/mod.rs
index f7573b2f7..435466f2e 100644
--- a/cli/src/commands/mod.rs
+++ b/cli/src/commands/mod.rs
@@ -46,6 +46,7 @@ mod restore;
 mod run;
 mod show;
 mod sparse;
+mod split;
 
 use std::fmt::Debug;
 use std::io::Write;
@@ -61,12 +62,11 @@ use jj_lib::merge::Merge;
 use jj_lib::merged_tree::{MergedTree, MergedTreeBuilder};
 use jj_lib::op_store::WorkspaceId;
 use jj_lib::repo::{ReadonlyRepo, Repo};
-use jj_lib::rewrite::{merge_commit_trees, DescendantRebaser};
+use jj_lib::rewrite::merge_commit_trees;
 use jj_lib::settings::UserSettings;
 use jj_lib::working_copy::SnapshotOptions;
 use jj_lib::workspace::{default_working_copy_initializer, Workspace};
 use jj_lib::{file_util, revset};
-use maplit::{hashmap, hashset};
 use tracing::instrument;
 
 use crate::cli_util::{
@@ -134,7 +134,7 @@ enum Commands {
     Show(show::ShowArgs),
     #[command(subcommand)]
     Sparse(sparse::SparseArgs),
-    Split(SplitArgs),
+    Split(split::SplitArgs),
     Squash(SquashArgs),
     Status(StatusArgs),
     #[command(subcommand)]
@@ -220,32 +220,6 @@ struct UnsquashArgs {
     interactive: bool,
 }
 
-/// Split a revision in two
-///
-/// Starts a diff editor (`meld` by default) on the changes in the revision.
-/// Edit the right side of the diff until it has the content you want in the
-/// first revision. Once you close the editor, your edited content will replace
-/// the previous revision. The remaining changes will be put in a new revision
-/// on top.
-///
-/// If the change you split had a description, you will be asked to enter a
-/// change description for each commit. If the change did not have a
-/// description, the second part will not get a description, and you will be
-/// asked for a description only for the first part.
-#[derive(clap::Args, Clone, Debug)]
-struct SplitArgs {
-    /// Interactively choose which parts to split. This is the default if no
-    /// paths are provided.
-    #[arg(long, short)]
-    interactive: bool,
-    /// The revision to split
-    #[arg(long, short, default_value = "@")]
-    revision: RevisionArg,
-    /// Put these paths in the first commit
-    #[arg(value_hint = clap::ValueHint::AnyPath)]
-    paths: Vec<String>,
-}
-
 /// Commands for working with workspaces
 ///
 /// Workspaces let you add additional working copies attached to the same repo.
@@ -845,33 +819,6 @@ fn description_template_for_commit(
     }
 }
 
-fn description_template_for_cmd_split(
-    ui: &Ui,
-    settings: &UserSettings,
-    workspace_command: &WorkspaceCommandHelper,
-    intro: &str,
-    overall_commit_description: &str,
-    from_tree: &MergedTree,
-    to_tree: &MergedTree,
-) -> Result<String, CommandError> {
-    let mut diff_summary_bytes = Vec::new();
-    diff_util::show_diff(
-        ui,
-        &mut PlainTextFormatter::new(&mut diff_summary_bytes),
-        workspace_command,
-        from_tree,
-        to_tree,
-        &EverythingMatcher,
-        &[DiffFormat::Summary],
-    )?;
-    let description = if overall_commit_description.is_empty() {
-        settings.default_description()
-    } else {
-        overall_commit_description.to_owned()
-    };
-    Ok(format!("JJ: {intro}\n{description}\n") + &diff_summary_to_description(&diff_summary_bytes))
-}
-
 fn diff_summary_to_description(bytes: &[u8]) -> String {
     let text = std::str::from_utf8(bytes).expect(
         "Summary diffs and repo paths must always be valid UTF8.",
@@ -881,109 +828,6 @@ fn diff_summary_to_description(bytes: &[u8]) -> String {
         + &textwrap::indent(text, "JJ:     ")
 }
 
-#[instrument(skip_all)]
-fn cmd_split(ui: &mut Ui, command: &CommandHelper, args: &SplitArgs) -> Result<(), CommandError> {
-    let mut workspace_command = command.workspace_helper(ui)?;
-    let commit = workspace_command.resolve_single_rev(&args.revision, ui)?;
-    workspace_command.check_rewritable([&commit])?;
-    let matcher = workspace_command.matcher_from_values(&args.paths)?;
-    let mut tx =
-        workspace_command.start_transaction(&format!("split commit {}", commit.id().hex()));
-    let end_tree = commit.tree()?;
-    let base_tree = merge_commit_trees(tx.repo(), &commit.parents())?;
-    let interactive = args.interactive || args.paths.is_empty();
-    let instructions = format!(
-        "\
-You are splitting a commit in two: {}
-
-The diff initially shows the changes in the commit you're splitting.
-
-Adjust the right side until it shows the contents you want for the first
-(parent) commit. The remainder will be in the second commit. If you
-don't make any changes, then the operation will be aborted.
-",
-        tx.format_commit_summary(&commit)
-    );
-    let tree_id = tx.select_diff(
-        ui,
-        &base_tree,
-        &end_tree,
-        matcher.as_ref(),
-        &instructions,
-        interactive,
-    )?;
-    if &tree_id == commit.tree_id() && interactive {
-        writeln!(ui.stderr(), "Nothing changed.")?;
-        return Ok(());
-    }
-    let middle_tree = tx.repo().store().get_root_tree(&tree_id)?;
-    if middle_tree.id() == base_tree.id() {
-        writeln!(
-            ui.warning(),
-            "The given paths do not match any file: {}",
-            args.paths.join(" ")
-        )?;
-    }
-
-    let first_template = description_template_for_cmd_split(
-        ui,
-        command.settings(),
-        tx.base_workspace_helper(),
-        "Enter commit description for the first part (parent).",
-        commit.description(),
-        &base_tree,
-        &middle_tree,
-    )?;
-    let first_description = edit_description(tx.base_repo(), &first_template, command.settings())?;
-    let first_commit = tx
-        .mut_repo()
-        .rewrite_commit(command.settings(), &commit)
-        .set_tree_id(tree_id)
-        .set_description(first_description)
-        .write()?;
-    let second_description = if commit.description().is_empty() {
-        // If there was no description before, don't ask for one for the second commit.
-        "".to_string()
-    } else {
-        let second_template = description_template_for_cmd_split(
-            ui,
-            command.settings(),
-            tx.base_workspace_helper(),
-            "Enter commit description for the second part (child).",
-            commit.description(),
-            &middle_tree,
-            &end_tree,
-        )?;
-        edit_description(tx.base_repo(), &second_template, command.settings())?
-    };
-    let second_commit = tx
-        .mut_repo()
-        .rewrite_commit(command.settings(), &commit)
-        .set_parents(vec![first_commit.id().clone()])
-        .set_tree_id(commit.tree_id().clone())
-        .generate_new_change_id()
-        .set_description(second_description)
-        .write()?;
-    let mut rebaser = DescendantRebaser::new(
-        command.settings(),
-        tx.mut_repo(),
-        hashmap! { commit.id().clone() => hashset!{second_commit.id().clone()} },
-        hashset! {},
-    );
-    rebaser.rebase_all()?;
-    let num_rebased = rebaser.rebased().len();
-    if num_rebased > 0 {
-        writeln!(ui.stderr(), "Rebased {num_rebased} descendant commits")?;
-    }
-    write!(ui.stderr(), "First part: ")?;
-    tx.write_commit_summary(ui.stderr_formatter().as_mut(), &first_commit)?;
-    write!(ui.stderr(), "\nSecond part: ")?;
-    tx.write_commit_summary(ui.stderr_formatter().as_mut(), &second_commit)?;
-    writeln!(ui.stderr())?;
-    tx.finish(ui)?;
-    Ok(())
-}
-
 fn make_branch_term(branch_names: &[impl fmt::Display]) -> String {
     match branch_names {
         [branch_name] => format!("branch {}", branch_name),
@@ -1304,7 +1148,7 @@ pub fn run_command(ui: &mut Ui, command_helper: &CommandHelper) -> Result<(), Co
         Commands::Restore(sub_args) => restore::cmd_restore(ui, command_helper, sub_args),
         Commands::Run(sub_args) => run::cmd_run(ui, command_helper, sub_args),
         Commands::Diffedit(sub_args) => diffedit::cmd_diffedit(ui, command_helper, sub_args),
-        Commands::Split(sub_args) => cmd_split(ui, command_helper, sub_args),
+        Commands::Split(sub_args) => split::cmd_split(ui, command_helper, sub_args),
         Commands::Merge(sub_args) => merge::cmd_merge(ui, command_helper, sub_args),
         Commands::Rebase(sub_args) => rebase::cmd_rebase(ui, command_helper, sub_args),
         Commands::Backout(sub_args) => backout::cmd_backout(ui, command_helper, sub_args),
diff --git a/cli/src/commands/split.rs b/cli/src/commands/split.rs
new file mode 100644
index 000000000..000047f90
--- /dev/null
+++ b/cli/src/commands/split.rs
@@ -0,0 +1,189 @@
+// Copyright 2020 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 std::io::Write;
+
+use jj_lib::backend::ObjectId;
+use jj_lib::matchers::EverythingMatcher;
+use jj_lib::merged_tree::MergedTree;
+use jj_lib::repo::Repo;
+use jj_lib::rewrite::{merge_commit_trees, DescendantRebaser};
+use jj_lib::settings::UserSettings;
+use maplit::{hashmap, hashset};
+use tracing::instrument;
+
+use super::{diff_summary_to_description, edit_description};
+use crate::cli_util::{CommandError, CommandHelper, RevisionArg, WorkspaceCommandHelper};
+use crate::diff_util::{self, DiffFormat};
+use crate::formatter::PlainTextFormatter;
+use crate::ui::Ui;
+
+/// Split a revision in two
+///
+/// Starts a diff editor (`meld` by default) on the changes in the revision.
+/// Edit the right side of the diff until it has the content you want in the
+/// first revision. Once you close the editor, your edited content will replace
+/// the previous revision. The remaining changes will be put in a new revision
+/// on top.
+///
+/// If the change you split had a description, you will be asked to enter a
+/// change description for each commit. If the change did not have a
+/// description, the second part will not get a description, and you will be
+/// asked for a description only for the first part.
+#[derive(clap::Args, Clone, Debug)]
+pub(crate) struct SplitArgs {
+    /// Interactively choose which parts to split. This is the default if no
+    /// paths are provided.
+    #[arg(long, short)]
+    interactive: bool,
+    /// The revision to split
+    #[arg(long, short, default_value = "@")]
+    revision: RevisionArg,
+    /// Put these paths in the first commit
+    #[arg(value_hint = clap::ValueHint::AnyPath)]
+    paths: Vec<String>,
+}
+
+#[instrument(skip_all)]
+pub(crate) fn cmd_split(
+    ui: &mut Ui,
+    command: &CommandHelper,
+    args: &SplitArgs,
+) -> Result<(), CommandError> {
+    let mut workspace_command = command.workspace_helper(ui)?;
+    let commit = workspace_command.resolve_single_rev(&args.revision, ui)?;
+    workspace_command.check_rewritable([&commit])?;
+    let matcher = workspace_command.matcher_from_values(&args.paths)?;
+    let mut tx =
+        workspace_command.start_transaction(&format!("split commit {}", commit.id().hex()));
+    let end_tree = commit.tree()?;
+    let base_tree = merge_commit_trees(tx.repo(), &commit.parents())?;
+    let interactive = args.interactive || args.paths.is_empty();
+    let instructions = format!(
+        "\
+You are splitting a commit in two: {}
+
+The diff initially shows the changes in the commit you're splitting.
+
+Adjust the right side until it shows the contents you want for the first
+(parent) commit. The remainder will be in the second commit. If you
+don't make any changes, then the operation will be aborted.
+",
+        tx.format_commit_summary(&commit)
+    );
+    let tree_id = tx.select_diff(
+        ui,
+        &base_tree,
+        &end_tree,
+        matcher.as_ref(),
+        &instructions,
+        interactive,
+    )?;
+    if &tree_id == commit.tree_id() && interactive {
+        writeln!(ui.stderr(), "Nothing changed.")?;
+        return Ok(());
+    }
+    let middle_tree = tx.repo().store().get_root_tree(&tree_id)?;
+    if middle_tree.id() == base_tree.id() {
+        writeln!(
+            ui.warning(),
+            "The given paths do not match any file: {}",
+            args.paths.join(" ")
+        )?;
+    }
+
+    let first_template = description_template_for_cmd_split(
+        ui,
+        command.settings(),
+        tx.base_workspace_helper(),
+        "Enter commit description for the first part (parent).",
+        commit.description(),
+        &base_tree,
+        &middle_tree,
+    )?;
+    let first_description = edit_description(tx.base_repo(), &first_template, command.settings())?;
+    let first_commit = tx
+        .mut_repo()
+        .rewrite_commit(command.settings(), &commit)
+        .set_tree_id(tree_id)
+        .set_description(first_description)
+        .write()?;
+    let second_description = if commit.description().is_empty() {
+        // If there was no description before, don't ask for one for the second commit.
+        "".to_string()
+    } else {
+        let second_template = description_template_for_cmd_split(
+            ui,
+            command.settings(),
+            tx.base_workspace_helper(),
+            "Enter commit description for the second part (child).",
+            commit.description(),
+            &middle_tree,
+            &end_tree,
+        )?;
+        edit_description(tx.base_repo(), &second_template, command.settings())?
+    };
+    let second_commit = tx
+        .mut_repo()
+        .rewrite_commit(command.settings(), &commit)
+        .set_parents(vec![first_commit.id().clone()])
+        .set_tree_id(commit.tree_id().clone())
+        .generate_new_change_id()
+        .set_description(second_description)
+        .write()?;
+    let mut rebaser = DescendantRebaser::new(
+        command.settings(),
+        tx.mut_repo(),
+        hashmap! { commit.id().clone() => hashset!{second_commit.id().clone()} },
+        hashset! {},
+    );
+    rebaser.rebase_all()?;
+    let num_rebased = rebaser.rebased().len();
+    if num_rebased > 0 {
+        writeln!(ui.stderr(), "Rebased {num_rebased} descendant commits")?;
+    }
+    write!(ui.stderr(), "First part: ")?;
+    tx.write_commit_summary(ui.stderr_formatter().as_mut(), &first_commit)?;
+    write!(ui.stderr(), "\nSecond part: ")?;
+    tx.write_commit_summary(ui.stderr_formatter().as_mut(), &second_commit)?;
+    writeln!(ui.stderr())?;
+    tx.finish(ui)?;
+    Ok(())
+}
+
+fn description_template_for_cmd_split(
+    ui: &Ui,
+    settings: &UserSettings,
+    workspace_command: &WorkspaceCommandHelper,
+    intro: &str,
+    overall_commit_description: &str,
+    from_tree: &MergedTree,
+    to_tree: &MergedTree,
+) -> Result<String, CommandError> {
+    let mut diff_summary_bytes = Vec::new();
+    diff_util::show_diff(
+        ui,
+        &mut PlainTextFormatter::new(&mut diff_summary_bytes),
+        workspace_command,
+        from_tree,
+        to_tree,
+        &EverythingMatcher,
+        &[DiffFormat::Summary],
+    )?;
+    let description = if overall_commit_description.is_empty() {
+        settings.default_description()
+    } else {
+        overall_commit_description.to_owned()
+    };
+    Ok(format!("JJ: {intro}\n{description}\n") + &diff_summary_to_description(&diff_summary_bytes))
+}