next/prev: make --edit implied when already on non-head commit

Users who edit non-head commits usually expect `jj next/prev` to
continue to edit the next/previous commit, so let's make that the
default behavior. This should not confuse users who don't edit
non-head commits since they will simply not be in this state. My main
concern is that doing `jj next; jj prev` will now usually take you
back to the previous commit, but not if you started on the parent of a
head commit.

CHANGELOG.md

@@ -32,6 +32,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * In the templating language, Timestamps now have a `.local()` method for
   converting to the local timezone.
 
+* `jj next/prev` now infer `--edit` when you're already editing a non-head
+  commit (a commit with children).
+
 ### Fixed bugs
 
 * On Windows, symlinks in the repo are now materialized as regular files in the

cli/src/commands/next.rs

@@ -48,6 +48,9 @@ use crate::ui::Ui;
 /// B => @
 /// |    |
 /// @    A
+///
+/// If your working-copy commit already has visible children, then `--edit` is
+/// implied.
 /// ```
 #[derive(clap::Args, Clone, Debug)]
 #[command(verbatim_doc_comment)]
@@ -100,11 +103,16 @@ pub(crate) fn cmd_next(
     args: &NextArgs,
 ) -> Result<(), CommandError> {
     let mut workspace_command = command.workspace_helper(ui)?;
-    let edit = args.edit;
     let amount = args.amount;
     let current_wc_id = workspace_command
         .get_wc_commit_id()
         .ok_or_else(|| user_error("This command requires a working copy"))?;
+    let edit = args.edit
+        || !workspace_command
+            .repo()
+            .view()
+            .heads()
+            .contains(current_wc_id);
     let current_wc = workspace_command.repo().store().get_commit(current_wc_id)?;
     // If we're editing, start at the working-copy commit.
     // Otherwise start from our direct parent.

cli/src/commands/prev.rs

@@ -29,7 +29,7 @@ use crate::ui::Ui;
 /// D @  D
 /// |/   |
 /// A => A @
-/// |    | /
+/// |    |/
 /// B    B
 /// ```
 ///
@@ -44,6 +44,9 @@ use crate::ui::Ui;
 /// B    B
 /// |    |
 /// A    A
+///
+/// If your working-copy commit already has visible children, then `--edit` is
+/// implied.
 /// ```
 // TODO(#2126): Handle multiple parents, e.g merges.
 #[derive(clap::Args, Clone, Debug)]
@@ -63,11 +66,16 @@ pub(crate) fn cmd_prev(
     args: &PrevArgs,
 ) -> Result<(), CommandError> {
     let mut workspace_command = command.workspace_helper(ui)?;
-    let edit = args.edit;
     let amount = args.amount;
     let current_wc_id = workspace_command
         .get_wc_commit_id()
         .ok_or_else(|| user_error("This command requires a working copy"))?;
+    let edit = args.edit
+        || !workspace_command
+            .repo()
+            .view()
+            .heads()
+            .contains(current_wc_id);
     let current_wc = workspace_command.repo().store().get_commit(current_wc_id)?;
     let start_id = if edit {
         current_wc_id

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

@@ -1145,6 +1145,9 @@ C    C
 B => @
 |    |
 @    A
+
+If your working-copy commit is already a non-head commit (i.e. if it has
+visible children), then `--edit` is implied.
 ```
 
 **Usage:** `jj next [OPTIONS] [AMOUNT]`
@@ -1330,7 +1333,7 @@ The command moves you to the parent in a linear fashion.
 D @  D
 |/   |
 A => A @
-|    | /
+|    |/
 B    B
 ```
 
@@ -1345,6 +1348,9 @@ C => @
 B    B
 |    |
 A    A
+
+If your working-copy commit is already a non-head commit (i.e. if it has
+visible children), then `--edit` is implied.
 ```
 
 **Usage:** `jj prev [OPTIONS] [AMOUNT]`

cli/tests/test_next_prev_commands.rs

@@ -284,6 +284,13 @@ fn test_prev_editing() {
     Working copy now at: zsuskuln 009f88bf (empty) fourth
     Parent commit      : kkmpptxz 3fa8931e (empty) third
     "###);
+    // --edit is implied when already editing a non-head commit
+    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["prev"]);
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @r###"
+    Working copy now at: yqosqzyt d2edc95b (empty) (no description set)
+    Parent commit      : rlvkpnrz 5c52832c (empty) second
+    "###);
 }
 
 #[test]
@@ -296,10 +303,17 @@ fn test_next_editing() {
     test_env.jj_cmd_ok(&repo_path, &["commit", "-m", "second"]);
     test_env.jj_cmd_ok(&repo_path, &["commit", "-m", "third"]);
     test_env.jj_cmd_ok(&repo_path, &["commit", "-m", "fourth"]);
-    test_env.jj_cmd_ok(&repo_path, &["edit", "@--"]);
+    test_env.jj_cmd_ok(&repo_path, &["edit", "@---"]);
     let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["next", "--edit"]);
     insta::assert_snapshot!(stdout, @"");
     insta::assert_snapshot!(stderr, @r###"
+    Working copy now at: kkmpptxz 3fa8931e (empty) third
+    Parent commit      : rlvkpnrz 5c52832c (empty) second
+    "###);
+    // --edit is implied when already editing a non-head commit
+    let (stdout, stderr) = test_env.jj_cmd_ok(&repo_path, &["next"]);
+    insta::assert_snapshot!(stdout, @"");
+    insta::assert_snapshot!(stderr, @r###"
     Working copy now at: zsuskuln 009f88bf (empty) fourth
     Parent commit      : kkmpptxz 3fa8931e (empty) third
     "###);