Feat: Don't abandon empty commits on partial squash.

If the user wrote, for example, `jj squash foo.rs`, it'd be a little wierd if we then moved a branch pointer to the parent commit.

Fixes #3815

CHANGELOG.md

@@ -64,6 +64,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   [#3800](https://github.com/martinvonz/jj/issues/3800) and
   [#3801](https://github.com/martinvonz/jj/issues/3801)).
 
+* 
+* `jj squash` now accepts a `--keep-empty` option to keep the source commit.
+
 ### Fixed bugs
 
 * Previously, `jj git push` only made sure that the branch is in the expected

cli/src/commands/move.rs

@@ -100,6 +100,7 @@ pub(crate) fn cmd_move(
         SquashedDescription::Combine,
         false,
         &args.paths,
+        false,
     )?;
     tx.finish(ui, tx_description)?;
     Ok(())

cli/src/commands/squash.rs

@@ -38,8 +38,8 @@ use crate::ui::Ui;
 /// commit to the grandparent.
 ///
 /// If, after moving changes out, the source revision is empty compared to its
-/// parent(s), it will be abandoned. Without `--interactive`, the source
-/// revision will always be empty.
+/// parent(s), and `--keep-empty` is not set, it will be abandoned. Without
+/// `--interactive` or paths, the source revision will always be empty.
 ///
 /// If the source became empty and both the source and destination had a
 /// non-empty description, you will be asked for the combined description. If
@@ -74,6 +74,9 @@ pub(crate) struct SquashArgs {
     /// Move only changes to these paths (instead of all paths)
     #[arg(conflicts_with_all = ["interactive", "tool"], value_hint = clap::ValueHint::AnyPath)]
     paths: Vec<String>,
+    /// The source revision will not be abandoned
+    #[arg(long)]
+    keep_empty: bool,
 }
 
 #[instrument(skip_all)]
@@ -132,6 +135,7 @@ pub(crate) fn cmd_squash(
         SquashedDescription::from_args(args),
         args.revision.is_none() && args.from.is_empty() && args.into.is_none(),
         &args.paths,
+        args.keep_empty,
     )?;
     tx.finish(ui, tx_description)?;
     Ok(())
@@ -157,7 +161,7 @@ impl SquashedDescription {
         if !args.message_paragraphs.is_empty() {
             let desc = join_message_paragraphs(&args.message_paragraphs);
             SquashedDescription::Exact(desc)
-        } else if args.use_destination_message {
+        } else if args.use_destination_message || args.keep_empty {
             SquashedDescription::UseDestination
         } else {
             SquashedDescription::Combine
@@ -177,6 +181,7 @@ pub fn move_diff(
     description: SquashedDescription,
     no_rev_arg: bool,
     path_arg: &[String],
+    keep_empty: bool,
 ) -> Result<(), CommandError> {
     tx.base_workspace_helper()
         .check_rewritable(sources.iter().chain(std::iter::once(destination)).ids())?;
@@ -210,7 +215,7 @@ from the source will be moved into the destination.
         let selected_tree_id =
             diff_selector.select(&parent_tree, &source_tree, matcher, Some(&instructions))?;
         let selected_tree = tx.repo().store().get_root_tree(&selected_tree_id)?;
-        let abandon = selected_tree.id() == source_tree.id();
+        let abandon = !keep_empty && selected_tree.id() == source_tree.id();
         if !abandon && selected_tree_id == parent_tree.id() {
             // Nothing selected from this commit. If it's abandoned (i.e. already empty), we
             // still include it so `jj squash` can be used for abandoning an empty commit in

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

@@ -1781,7 +1781,7 @@ With the `-r` option, moves the changes from the specified revision to the paren
 
 With the `--from` and/or `--into` options, moves changes from/to the given revisions. If either is left out, it defaults to the working-copy commit. For example, `jj squash --into @--` moves changes from the working-copy commit to the grandparent.
 
-If, after moving changes out, the source revision is empty compared to its parent(s), it will be abandoned. Without `--interactive`, the source revision will always be empty.
+If, after moving changes out, the source revision is empty compared to its parent(s), and `--keep-empty` is not set, it will be abandoned. Without `--interactive` or paths, the source revision will always be empty.
 
 If the source became empty and both the source and destination had a non-empty description, you will be asked for the combined description. If either was empty, then the other one will be used.
 
@@ -1808,6 +1808,10 @@ If a working-copy commit gets abandoned, it will be given a new, empty commit. T
   Possible values: `true`, `false`
 
 * `--tool <NAME>` — Specify diff editor to be used (implies --interactive)
+* `--keep-empty` — The source revision will not be abandoned
+
+  Possible values: `true`, `false`
+
 
 
 

cli/tests/test_squash_command.rs

@@ -259,6 +259,47 @@ fn test_squash_partial() {
     insta::assert_snapshot!(stdout, @"");
 }
 
+#[test]
+fn test_squash_keep_empty() {
+    let test_env = TestEnvironment::default();
+    test_env.jj_cmd_ok(test_env.env_root(), &["git", "init", "repo"]);
+    let repo_path = test_env.env_root().join("repo");
+
+    test_env.jj_cmd_ok(&repo_path, &["branch", "create", "a"]);
+    std::fs::write(repo_path.join("file1"), "a\n").unwrap();
+    test_env.jj_cmd_ok(&repo_path, &["new"]);
+    test_env.jj_cmd_ok(&repo_path, &["branch", "create", "b"]);
+    std::fs::write(repo_path.join("file1"), "b\n").unwrap();
+    test_env.jj_cmd_ok(&repo_path, &["new"]);
+    test_env.jj_cmd_ok(&repo_path, &["branch", "create", "c"]);
+    std::fs::write(repo_path.join("file1"), "c\n").unwrap();
+    // Test the setup
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    @  90fe0a96fc90 c
+    ◉  fa5efbdf533c b
+    ◉  90aeefd03044 a
+    ◉  000000000000
+    "###);
+
+    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["squash", "-r", "b", "--keep-empty"]);
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @r###"
+    Rebased 2 descendant commits
+    Working copy now at: mzvwutvl 8d072ade c | (no description set)
+    Parent commit      : kkmpptxz 1ffda862 b | (empty) (no description set)
+    "###);
+    insta::assert_snapshot!(get_log_output(&test_env, &repo_path), @r###"
+    @  8d072adecae0 c
+    ◉  1ffda862e07e b
+    ◉  297fde616b71 a
+    ◉  000000000000
+    "###);
+    let stdout = test_env.jj_cmd_success(&repo_path, &["print", "file1", "-r", "a"]);
+    insta::assert_snapshot!(stdout, @r###"
+    b
+    "###);
+}
+
 #[test]
 fn test_squash_from_to() {
     let test_env = TestEnvironment::default();