Add config flag to control prev/next edit behaviour.

The flag is a tristate flag where:
  - Auto - Maintain current behaviour. This edits if
    the wc parent is not a head commit. Else, it will
    create a new commit on the parent of the wc in
    the direction of movement.
  - Always - Always edit
  - Never - Never edit, prefer the new+squash workflow.

Part of #3947

CHANGELOG.md

@@ -65,6 +65,10 @@ to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### New features
 
+* Add new config knob, `ui.movement.edit` for controlling the behaviour of `prev/next`.
+  `auto` maintains existing behaviour while `always` and `never` turn `edit` mode
+  permanently `on` and `off` respectively.
+
 * Define `immutable_heads()` revset alias in terms of a new `builtin_immutable_heads()`.
   This enables users to redefine `immutable_heads()` as they wish, but still
   have `builtin_immutable_heads()` which should not be redefined.

cli/src/commands/next.rs

@@ -14,7 +14,7 @@
 
 use crate::cli_util::{short_commit_hash, CommandHelper};
 use crate::command_error::{user_error, CommandError};
-use crate::movement_util::{get_target_commit, Direction};
+use crate::movement_util::{get_movement_edit_mode, get_target_commit, Direction};
 use crate::ui::Ui;
 
 /// Move the working-copy commit to the child revision
@@ -73,12 +73,12 @@ pub(crate) fn cmd_next(
     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 wc_is_head = workspace_command
+        .repo()
+        .view()
+        .heads()
+        .contains(current_wc_id);
+    let edit = get_movement_edit_mode(ui, args.edit, wc_is_head);
     let target = get_target_commit(
         ui,
         &workspace_command,

cli/src/commands/prev.rs

@@ -14,7 +14,7 @@
 
 use crate::cli_util::{short_commit_hash, CommandHelper};
 use crate::command_error::{user_error, CommandError};
-use crate::movement_util::{get_target_commit, Direction};
+use crate::movement_util::{get_movement_edit_mode, get_target_commit, Direction};
 use crate::ui::Ui;
 /// Change the working copy revision relative to the parent revision
 ///
@@ -69,12 +69,12 @@ pub(crate) fn cmd_prev(
     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 wc_is_head = workspace_command
+        .repo()
+        .view()
+        .heads()
+        .contains(current_wc_id);
+    let edit = get_movement_edit_mode(ui, args.edit, wc_is_head);
     let target = get_target_commit(
         ui,
         &workspace_command,

cli/src/config/misc.toml

@@ -18,5 +18,8 @@ pager = { command = ["less", "-FRX"], env = { LESSCHARSET = "utf-8" } }
 log-word-wrap = false
 log-synthetic-elided-nodes = true
 
+[ui.movement]
+edit = "auto"
+
 [snapshot]
 max-new-file-size = "1MiB"

cli/src/movement_util.rs

@@ -23,7 +23,7 @@ use jj_lib::revset::{RevsetExpression, RevsetFilterPredicate, RevsetIteratorExt}
 
 use crate::cli_util::WorkspaceCommandHelper;
 use crate::command_error::{user_error, CommandError};
-use crate::ui::Ui;
+use crate::ui::{MovementEditMode, Ui};
 
 pub enum Direction {
     Next,
@@ -98,6 +98,14 @@ impl Direction {
     }
 }
 
+pub fn get_movement_edit_mode(ui: &Ui, cli_edit_flag: bool, wc_is_head: bool) -> bool {
+    match ui.movement_edit_mode() {
+        MovementEditMode::Always => true,
+        MovementEditMode::Auto => cli_edit_flag || !wc_is_head,
+        MovementEditMode::Never => false,
+    }
+}
+
 pub fn get_target_commit(
     ui: &mut Ui,
     workspace_command: &WorkspaceCommandHelper,

cli/src/ui.rs

@@ -236,13 +236,35 @@ impl Write for UiStderr<'_> {
     }
 }
 
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq, serde::Deserialize)]
+#[serde(rename_all(deserialize = "kebab-case"))]
+pub enum MovementEditMode {
+    #[default]
+    Auto,
+    Always,
+    Never,
+}
+
+fn movement_settings(config: &config::Config) -> Result<MovementSettings, CommandError> {
+    config
+        .get::<MovementSettings>("ui.movement")
+        .map_err(|err| config_error_with_message("Invalid `ui.movement`", err))
+}
+
+#[derive(Clone, Copy, Debug, Default, Eq, PartialEq, serde::Deserialize)]
+#[serde(rename_all(deserialize = "kebab-case"))]
+pub struct MovementSettings {
+    edit: MovementEditMode,
+}
+
 pub struct Ui {
     quiet: bool,
     pager_cmd: CommandNameAndArgs,
     paginate: PaginationChoice,
     progress_indicator: bool,
     formatter_factory: FormatterFactory,
     output: UiOutput,
+    movement: MovementSettings,
 }
 
 fn progress_indicator_setting(config: &config::Config) -> bool {
@@ -349,6 +371,7 @@ impl Ui {
             pager_cmd: pager_setting(config)?,
             paginate: pagination_setting(config)?,
             progress_indicator,
+            movement: movement_settings(config)?,
             output: UiOutput::new_terminal(),
         })
     }
@@ -359,6 +382,7 @@ impl Ui {
         self.pager_cmd = pager_setting(config)?;
         self.progress_indicator = progress_indicator_setting(config);
         self.formatter_factory = prepare_formatter_factory(config, &io::stdout())?;
+        self.movement = movement_settings(config)?;
         Ok(())
     }
 
@@ -397,6 +421,10 @@ impl Ui {
         }
     }
 
+    pub fn movement_edit_mode(&self) -> MovementEditMode {
+        self.movement.edit.to_owned()
+    }
+
     pub fn color(&self) -> bool {
         self.formatter_factory.is_color()
     }