split: do not prevent all changes from going into the parent commit

CHANGELOG.md

@@ -87,6 +87,10 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 * `jj diffedit`, `jj abandon`, and `jj restore` now accept a `--restore-descendants`
   flag. When used, descendants of the edited or deleted commits will keep their original
   content.
+
+* `jj split` now lets the user select all changes in interactive mode. This may be used
+  to move all changes into a parent commit while preserving the current commit
+  description.
 
 ### Fixed bugs
 

cli/src/commands/split.rs

@@ -109,17 +109,17 @@ the operation will be aborted.
     // Prompt the user to select the changes they want for the first commit.
     let selected_tree_id =
         diff_selector.select(&base_tree, &end_tree, matcher.as_ref(), format_instructions)?;
-    if &selected_tree_id == commit.tree_id() && diff_selector.is_interactive() {
+    if &selected_tree_id == commit.tree_id() {
         // The user selected everything from the original commit.
-        writeln!(ui.status(), "Nothing changed.")?;
-        return Ok(());
-    }
-    if selected_tree_id == base_tree.id() {
+        writeln!(
+            ui.warning_default(),
+            "All changes have been selected, the child commit will be empty"
+        )?;
+    } else if selected_tree_id == base_tree.id() {
         // The user selected nothing, so the first commit will be empty.
         writeln!(
             ui.warning_default(),
-            "The given paths do not match any file: {}",
-            args.paths.join(" ")
+            "No changes have been selected, the parent commit will be empty"
         )?;
     }
 

cli/tests/test_split_command.rs

@@ -102,13 +102,14 @@ fn test_split_by_paths() {
     test_env.set_up_fake_editor();
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["split", "-r", "@-", "."]);
     insta::assert_snapshot!(stdout, @"");
-    insta::assert_snapshot!(stderr, @r###"
+    insta::assert_snapshot!(stderr, @r#"
+    Warning: All changes have been selected, the child commit will be empty
     Rebased 1 descendant commits
     First part: qpvuntsm 9da0eea0 (no description set)
     Second part: znkkpsqq 5b5714a3 (empty) (no description set)
     Working copy now at: zsuskuln 0c798ee7 (no description set)
     Parent commit      : znkkpsqq 5b5714a3 (empty) (no description set)
-    "###);
+    "#);
 
     insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
     @  zsuskulnrvyr false
@@ -129,14 +130,14 @@ fn test_split_by_paths() {
     test_env.set_up_fake_editor();
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["split", "-r", "@-", "nonexistent"]);
     insta::assert_snapshot!(stdout, @"");
-    insta::assert_snapshot!(stderr, @r###"
-    Warning: The given paths do not match any file: nonexistent
+    insta::assert_snapshot!(stderr, @r#"
+    Warning: No changes have been selected, the parent commit will be empty
     Rebased 1 descendant commits
     First part: qpvuntsm bd42f95a (empty) (no description set)
     Second part: lylxulpl ed55c86b (no description set)
     Working copy now at: zsuskuln 1e1ed741 (no description set)
     Parent commit      : lylxulpl ed55c86b (no description set)
-    "###);
+    "#);
 
     insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
     @  zsuskulnrvyr false