ui: make hint_*() methods return Option

Same reasoning as the previous patch: we can avoid doing work when
`--quiet` is passed.

cli/src/cli_util.rs

@@ -1614,13 +1614,15 @@ pub fn print_checkout_stats(
              working copy.",
             stats.skipped_files
         )?;
-        writeln!(
-            ui.hint_default(),
-            "Inspect the changes compared to the intended target with `jj diff --from {}`.
+        if let Some(mut writer) = ui.hint_default() {
+            writeln!(
+                writer,
+                "Inspect the changes compared to the intended target with `jj diff --from {}`.
 Discard the conflicting changes with `jj restore --from {}`.",
-            short_commit_hash(new_commit.id()),
-            short_commit_hash(new_commit.id())
-        )?;
+                short_commit_hash(new_commit.id()),
+                short_commit_hash(new_commit.id())
+            )?;
+        }
     }
     Ok(())
 }
@@ -1641,21 +1643,25 @@ pub fn print_trackable_remote_branches(ui: &Ui, view: &View) -> io::Result<()> {
         return Ok(());
     }
 
-    writeln!(
-        ui.hint_default(),
-        "The following remote branches aren't associated with the existing local branches:"
-    )?;
+    if let Some(mut writer) = ui.hint_default() {
+        writeln!(
+            writer,
+            "The following remote branches aren't associated with the existing local branches:"
+        )?;
+    }
     if let Some(mut formatter) = ui.status_formatter() {
         for full_name in &remote_branch_names {
             write!(formatter, "  ")?;
             writeln!(formatter.labeled("branch"), "{full_name}")?;
         }
     }
-    writeln!(
-        ui.hint_default(),
-        "Run `jj branch track {names}` to keep local branches updated on future pulls.",
-        names = remote_branch_names.join(" "),
-    )?;
+    if let Some(mut writer) = ui.hint_default() {
+        writeln!(
+            writer,
+            "Run `jj branch track {names}` to keep local branches updated on future pulls.",
+            names = remote_branch_names.join(" "),
+        )?;
+    }
     Ok(())
 }
 
@@ -2197,14 +2203,14 @@ fn resolve_default_command(
         if matches.subcommand_name().is_none() {
             let args = get_string_or_array(config, "ui.default-command").optional()?;
             if args.is_none() {
-                writeln!(
-                    ui.hint_default(),
-                    "Use `jj -h` for a list of available commands."
-                )?;
-                writeln!(
-                    ui.hint_no_heading(),
-                    "Run `jj config set --user ui.default-command log` to disable this message."
-                )?;
+                if let Some(mut writer) = ui.hint_default() {
+                    writeln!(writer, "Use `jj -h` for a list of available commands.")?;
+                    writeln!(
+                        writer,
+                        "Run `jj config set --user ui.default-command log` to disable this \
+                         message."
+                    )?;
+                }
             }
             let default_command = args.unwrap_or_else(|| vec!["log".to_string()]);
 

cli/src/commands/branch.rs

@@ -321,12 +321,14 @@ fn cmd_branch_rename(
             ui.warning_default(),
             "Branch {old_branch} has tracking remote branches which were not renamed."
         )?;
-        writeln!(
-            ui.hint_default(),
-            "to rename the branch on the remote, you can `jj git push --branch {old_branch}` \
-             first (to delete it on the remote), and then `jj git push --branch {new_branch}`. \
-             `jj git push --all` would also be sufficient."
-        )?;
+        if let Some(mut writer) = ui.hint_default() {
+            writeln!(
+                writer,
+                "to rename the branch on the remote, you can `jj git push --branch {old_branch}` \
+                 first (to delete it on the remote), and then `jj git push --branch \
+                 {new_branch}`. `jj git push --all` would also be sufficient."
+            )?;
+        }
     }
 
     Ok(())

cli/src/commands/git.rs

@@ -595,10 +595,9 @@ fn get_default_fetch_remotes(
     } else if let Some(remote) = get_single_remote(git_repo)? {
         // if nothing was explicitly configured, try to guess
         if remote != DEFAULT_REMOTE {
-            writeln!(
-                ui.hint_default(),
-                "Fetching from the only existing remote: {remote}"
-            )?;
+            if let Some(mut writer) = ui.hint_default() {
+                writeln!(writer, "Fetching from the only existing remote: {remote}")?;
+            }
         }
         Ok(vec![remote])
     } else {
@@ -1038,10 +1037,9 @@ fn get_default_push_remote(
     } else if let Some(remote) = get_single_remote(git_repo)? {
         // similar to get_default_fetch_remotes
         if remote != DEFAULT_REMOTE {
-            writeln!(
-                ui.hint_default(),
-                "Pushing to the only existing remote: {remote}"
-            )?;
+            if let Some(mut writer) = ui.hint_default() {
+                writeln!(writer, "Pushing to the only existing remote: {remote}")?;
+            }
         }
         Ok(remote)
     } else {
@@ -1059,7 +1057,9 @@ impl RejectedBranchUpdateReason {
     fn print(&self, ui: &Ui) -> io::Result<()> {
         writeln!(ui.warning_default(), "{}", self.message)?;
         if let Some(hint) = &self.hint {
-            writeln!(ui.hint_default(), "{hint}")?;
+            if let Some(mut writer) = ui.hint_default() {
+                writeln!(writer, "{hint}")?;
+            }
         }
         Ok(())
     }

cli/src/commands/util.rs

@@ -128,16 +128,16 @@ fn cmd_util_completion(
     args: &UtilCompletionArgs,
 ) -> Result<(), CommandError> {
     let mut app = command.app().clone();
-    let warn = |shell| {
+    let warn = |shell| -> std::io::Result<()> {
         writeln!(
             ui.warning_default(),
             "`jj util completion --{shell}` will be removed in a future version, and this will be \
              a hard error"
         )?;
-        writeln!(
-            ui.hint_default(),
-            "Use `jj util completion {shell}` instead"
-        )
+        if let Some(mut writer) = ui.hint_default() {
+            writeln!(writer, "Use `jj util completion {shell}` instead")?;
+        }
+        Ok(())
     };
     let shell = match (args.shell, args.fish, args.zsh, args.bash) {
         (Some(s), false, false, false) => s,

cli/src/git_util.rs

@@ -409,12 +409,14 @@ pub fn print_failed_git_export(
             .iter()
             .any(|failed| matches!(failed.reason, FailedRefExportReason::FailedToSet(_)))
         {
-            writeln!(
-                ui.hint_default(),
-                r#"Git doesn't allow a branch name that looks like a parent directory of
+            if let Some(mut writer) = ui.hint_default() {
+                writeln!(
+                    writer,
+                    r#"Git doesn't allow a branch name that looks like a parent directory of
 another (e.g. `foo` and `foo/bar`). Try to rename the branches that failed to
 export or their "parent" branches."#,
-            )?;
+                )?;
+            }
         }
     }
     Ok(())

cli/src/merge_tools/mod.rs

@@ -123,12 +123,14 @@ fn editor_args_from_settings(
         Ok(args)
     } else {
         let default_editor = BUILTIN_EDITOR_NAME;
-        writeln!(
-            ui.hint_default(),
-            "Using default editor '{default_editor}'; run `jj config set --user {key} :builtin` \
-             to disable this message."
-        )
-        .ok();
+        if let Some(mut writer) = ui.hint_default() {
+            writeln!(
+                writer,
+                "Using default editor '{default_editor}'; run `jj config set --user {key} \
+                 :builtin` to disable this message."
+            )
+            .ok();
+        }
         Ok(default_editor.into())
     }
 }

cli/src/ui.rs

@@ -388,21 +388,25 @@ impl Ui {
     /// Writer to print hint with the default "Hint: " heading.
     pub fn hint_default(
         &self,
-    ) -> HeadingLabeledWriter<Box<dyn Formatter + '_>, &'static str, &'static str> {
+    ) -> Option<HeadingLabeledWriter<Box<dyn Formatter + '_>, &'static str, &'static str>> {
         self.hint_with_heading("Hint: ")
     }
 
     /// Writer to print hint without the "Hint: " heading.
-    pub fn hint_no_heading(&self) -> LabeledWriter<Box<dyn Formatter + '_>, &'static str> {
-        LabeledWriter::new(self.stderr_formatter(), "hint")
+    pub fn hint_no_heading(&self) -> Option<LabeledWriter<Box<dyn Formatter + '_>, &'static str>> {
+        Some(LabeledWriter::new(self.stderr_formatter(), "hint"))
     }
 
     /// Writer to print hint with the given heading.
     pub fn hint_with_heading<H: fmt::Display>(
         &self,
         heading: H,
-    ) -> HeadingLabeledWriter<Box<dyn Formatter + '_>, &'static str, H> {
-        HeadingLabeledWriter::new(self.stderr_formatter(), "hint", heading)
+    ) -> Option<HeadingLabeledWriter<Box<dyn Formatter + '_>, &'static str, H>> {
+        Some(HeadingLabeledWriter::new(
+            self.stderr_formatter(),
+            "hint",
+            heading,
+        ))
     }
 
     /// Writer to print warning with the default "Warning: " heading.