cli: make pager configurable per command

Allow `ui.pager` to be set as a table like so:

    [ui]
    pager.status = ":none"
    pager.log = { command = ["less", "-FRX"], env = { LESSCHARSET = "utf-8" } }
    pager.diff = ["delta", "..."]
    pager.default = "..."

`ui.pager.log` is used for `jj log`, `ui.pager.diff` for `jj diff`,
etc. The full name of the highest level subcommand is used, i.e. `jj
operation diff` uses `ui.pager.operation`. The value ":none" disables
paging for the selected command. If a command is not specifically
mentioned, the value of `ui.pager.default` is used.

The old behaviour is unchanged, i.e. `ui.pager = ["less", "-FRX"]` will
set the pager for all subcommands.

cli/src/command_error.rs

@@ -884,7 +884,7 @@ fn handle_clap_error(ui: &mut Ui, err: &clap::Error, hints: &[ErrorHint]) -> io:
 
     match err.kind() {
         clap::error::ErrorKind::DisplayHelp
-        | clap::error::ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand => ui.request_pager(),
+        | clap::error::ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand => ui.request_pager(""),
         _ => {}
     };
     // Definitions for exit codes and streams come from

cli/src/commands/bookmark/list.rs

@@ -148,7 +148,7 @@ pub fn cmd_bookmark_list(
             .labeled("bookmark_list")
     };
 
-    ui.request_pager();
+    ui.request_pager("bookmark");
     let mut formatter = ui.stdout_formatter();
 
     let mut found_deleted_local_bookmark = false;

cli/src/commands/config/list.rs

@@ -89,7 +89,7 @@ pub fn cmd_config_list(
     }
 
     if !annotated_values.is_empty() {
-        ui.request_pager();
+        ui.request_pager("config");
         let mut formatter = ui.stdout_formatter();
         for annotated in &annotated_values {
             template.format(annotated, formatter.as_mut())?;

cli/src/commands/diff.rs

@@ -123,7 +123,7 @@ pub(crate) fn cmd_diff(
     }
 
     let diff_renderer = workspace_command.diff_renderer_for(&args.format)?;
-    ui.request_pager();
+    ui.request_pager("diff");
     diff_renderer.show_diff(
         ui,
         ui.stdout_formatter().as_mut(),

cli/src/commands/evolog.rs

@@ -119,7 +119,7 @@ pub(crate) fn cmd_evolog(
             .labeled("node");
     }
 
-    ui.request_pager();
+    ui.request_pager("evolog");
     let mut formatter = ui.stdout_formatter();
     let formatter = formatter.as_mut();
 

cli/src/commands/file/annotate.rs

@@ -97,7 +97,7 @@ fn render_file_annotation(
     template_render: &TemplateRenderer<Commit>,
     annotation: &FileAnnotation,
 ) -> Result<(), CommandError> {
-    ui.request_pager();
+    ui.request_pager("file");
     let mut formatter = ui.stdout_formatter();
     for (line_no, (commit_id, line)) in annotation.lines().enumerate() {
         let commit_id = commit_id.expect("should reached to the empty ancestor");

cli/src/commands/file/list.rs

@@ -51,7 +51,7 @@ pub(crate) fn cmd_file_list(
     let matcher = workspace_command
         .parse_file_patterns(ui, &args.paths)?
         .to_matcher();
-    ui.request_pager();
+    ui.request_pager("file");
     for (name, _value) in tree.entries_matching(matcher.as_ref()) {
         writeln!(
             ui.stdout(),

cli/src/commands/file/show.rs

@@ -83,14 +83,14 @@ pub(crate) fn cmd_file_show(
             return Err(user_error(format!("No such path: {ui_path}")));
         }
         if !value.is_tree() {
-            ui.request_pager();
+            ui.request_pager("file");
             write_tree_entries(ui, &workspace_command, [(path, Ok(value))])?;
             return Ok(());
         }
     }
 
     let matcher = fileset_expression.to_matcher();
-    ui.request_pager();
+    ui.request_pager("file");
     write_tree_entries(
         ui,
         &workspace_command,

cli/src/commands/help.rs

@@ -52,7 +52,7 @@ pub(crate) fn cmd_help(
 ) -> Result<(), CommandError> {
     if let Some(name) = &args.keyword {
         let keyword = find_keyword(name).expect("clap should check this with `value_parser`");
-        ui.request_pager();
+        ui.request_pager("help");
         write!(ui.stdout(), "{}", keyword.content)?;
 
         return Ok(());

cli/src/commands/interdiff.rs

@@ -78,7 +78,7 @@ pub(crate) fn cmd_interdiff(
         .parse_file_patterns(ui, &args.paths)?
         .to_matcher();
     let diff_renderer = workspace_command.diff_renderer_for(&args.format)?;
-    ui.request_pager();
+    ui.request_pager("interdiff");
     diff_renderer.show_inter_diff(
         ui,
         ui.stdout_formatter().as_mut(),

cli/src/commands/log.rs

@@ -173,7 +173,7 @@ pub(crate) fn cmd_log(
     }
 
     {
-        ui.request_pager();
+        ui.request_pager("log");
         let mut formatter = ui.stdout_formatter();
         let formatter = formatter.as_mut();
 

cli/src/commands/operation/diff.rs

@@ -137,7 +137,7 @@ pub fn cmd_op_diff(
     };
 
     let op_summary_template = workspace_command.operation_summary_template();
-    ui.request_pager();
+    ui.request_pager("operation");
     let mut formatter = ui.stdout_formatter();
     write!(formatter, "From operation: ")?;
     op_summary_template.format(&from_op, &mut *formatter)?;

cli/src/commands/operation/log.rs

@@ -186,7 +186,7 @@ fn do_op_log(
         None
     };
 
-    ui.request_pager();
+    ui.request_pager("operation");
     let mut formatter = ui.stdout_formatter();
     let formatter = formatter.as_mut();
     let limit = args.limit.unwrap_or(usize::MAX);

cli/src/commands/operation/show.rs

@@ -93,7 +93,7 @@ pub fn cmd_op_show(
             .labeled("operation")
     };
 
-    ui.request_pager();
+    ui.request_pager("operation");
     let mut formatter = ui.stdout_formatter();
     template.format(&op, formatter.as_mut())?;
 

cli/src/commands/show.rs

@@ -59,7 +59,7 @@ pub(crate) fn cmd_show(
     };
     let template = workspace_command.parse_commit_template(ui, &template_string)?;
     let diff_renderer = workspace_command.diff_renderer_for(&args.format)?;
-    ui.request_pager();
+    ui.request_pager("show");
     let mut formatter = ui.stdout_formatter();
     let formatter = formatter.as_mut();
     template.format(&commit, formatter)?;

cli/src/commands/status.rs

@@ -58,7 +58,7 @@ pub(crate) fn cmd_status(
     let matcher = workspace_command
         .parse_file_patterns(ui, &args.paths)?
         .to_matcher();
-    ui.request_pager();
+    ui.request_pager("status");
     let mut formatter = ui.stdout_formatter();
     let formatter = formatter.as_mut();
 

cli/src/commands/tag.rs

@@ -76,7 +76,7 @@ fn cmd_tag_list(
             .labeled("tag_list")
     };
 
-    ui.request_pager();
+    ui.request_pager("tag");
     let mut formatter = ui.stdout_formatter();
 
     for (name, target) in view.tags() {

cli/src/ui.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::collections::HashMap;
 use std::env;
 use std::error;
 use std::fmt;
@@ -49,6 +50,7 @@ use crate::formatter::LabeledWriter;
 use crate::formatter::PlainTextFormatter;
 
 const BUILTIN_PAGER_NAME: &str = ":builtin";
+const BUILTIN_PAGER_NONE_NAME: &str = ":none";
 
 enum UiOutput {
     Terminal {
@@ -257,13 +259,28 @@ impl Write for UiStderr<'_> {
 
 pub struct Ui {
     quiet: bool,
-    pager_cmd: CommandNameAndArgs,
+    pager_cmd: PagerCmd,
     paginate: PaginationChoice,
     progress_indicator: bool,
     formatter_factory: FormatterFactory,
     output: UiOutput,
 }
 
+enum PagerCmd {
+    Default(CommandNameAndArgs),
+    PerSubcommand(HashMap<String, CommandNameAndArgs>),
+}
+
+impl PagerCmd {
+    fn from_config(config: &StackedConfig) -> Result<Self, ConfigGetError> {
+        const KEY: &str = "ui.pager";
+        config
+            .get(KEY)
+            .map(Self::Default)
+            .or_else(|_| config.get(KEY).map(Self::PerSubcommand))
+    }
+}
+
 #[derive(Clone, Copy, Debug, Default, Eq, PartialEq, serde::Deserialize)]
 #[serde(rename_all = "kebab-case")]
 pub enum ColorChoice {
@@ -333,7 +350,7 @@ impl Ui {
         Ok(Ui {
             quiet: config.get("ui.quiet")?,
             formatter_factory,
-            pager_cmd: config.get("ui.pager")?,
+            pager_cmd: PagerCmd::from_config(config)?,
             paginate: config.get("ui.paginate")?,
             progress_indicator: config.get("ui.progress-indicator")?,
             output: UiOutput::new_terminal(),
@@ -343,7 +360,7 @@ impl Ui {
     pub fn reset(&mut self, config: &StackedConfig) -> Result<(), CommandError> {
         self.quiet = config.get("ui.quiet")?;
         self.paginate = config.get("ui.paginate")?;
-        self.pager_cmd = config.get("ui.pager")?;
+        self.pager_cmd = PagerCmd::from_config(config)?;
         self.progress_indicator = config.get("ui.progress-indicator")?;
         self.formatter_factory = prepare_formatter_factory(config, &io::stdout())?;
         Ok(())
@@ -351,7 +368,7 @@ impl Ui {
 
     /// Switches the output to use the pager, if allowed.
     #[instrument(skip_all)]
-    pub fn request_pager(&mut self) {
+    pub fn request_pager(&mut self, subcommand: &str) {
         match self.paginate {
             PaginationChoice::Never => return,
             PaginationChoice::Auto => {}
@@ -360,25 +377,37 @@ impl Ui {
             return;
         }
 
-        let use_builtin_pager = matches!(
-            &self.pager_cmd, CommandNameAndArgs::String(name) if name == BUILTIN_PAGER_NAME);
-        let new_output = if use_builtin_pager {
-            Some(UiOutput::new_builtin())
-        } else {
-            UiOutput::new_paged(&self.pager_cmd)
-                .inspect_err(|err| {
-                    // The pager executable couldn't be found or couldn't be run
-                    writeln!(
-                        self.warning_default(),
-                        "Failed to spawn pager '{name}': {err}",
-                        name = self.pager_cmd.split_name(),
-                        err = format_error_with_sources(err),
-                    )
-                    .ok();
-                    writeln!(self.hint_default(), "Consider using the `:builtin` pager.").ok();
-                })
-                .ok()
+        let show_err = |cmd: &CommandNameAndArgs, err: &_| {
+            writeln!(
+                self.warning_default(),
+                "Failed to spawn pager '{name}': {err}",
+                name = cmd.split_name(),
+                err = format_error_with_sources(err)
+            )
+            .ok();
+            writeln!(self.hint_default(), "Consider using the `:builtin` pager.").ok();
         };
+
+        let new_output = match &self.pager_cmd {
+            PagerCmd::Default(CommandNameAndArgs::String(name)) if name == BUILTIN_PAGER_NAME => {
+                Some(UiOutput::new_builtin())
+            }
+            PagerCmd::Default(cmd) => UiOutput::new_paged(cmd)
+                .inspect_err(|err| show_err(cmd, err))
+                .ok(),
+            PagerCmd::PerSubcommand(map) => {
+                match map.get(subcommand).or_else(|| map.get("default")) {
+                    Some(CommandNameAndArgs::String(name)) if name == BUILTIN_PAGER_NONE_NAME => {
+                        None
+                    }
+                    Some(cmd) => UiOutput::new_paged(cmd)
+                        .inspect_err(|err| show_err(cmd, err))
+                        .ok(),
+                    None => None,
+                }
+            }
+        };
+
         if let Some(output) = new_output {
             self.output = output;
         }

docs/config.md

@@ -578,6 +578,22 @@ pager = "delta"
 format = "git"
 ```
 
+### Setting the pager per subcommand
+
+A different pager can be configured for each subcommand by using a table. For
+example:
+
+```toml
+[ui]
+# set to ":none" to disable paging for a command
+pager.status = ":none"
+pager.log = { command = ["less", "-FRX"], env = { LESSCHARSET = "utf-8" } }
+pager.diff = ["delta", "--dark"]
+
+# use pager.default for all subcommands not otherwise mentioned
+pager.default = ":builtin"
+```
+
 ## Aliases
 
 You can define aliases for commands, including their arguments. For example: