cli: render string pattern suggestion as a hint

Templater doesn't have the one yet, but I think it belongs to the same
category.

For clap::Error, we could use clap's own mechanism to render suggestions as
"tip: ...", but I feel "Hint: ..." looks better because our error/hint message
is capitalized.

cli/src/command_error.rs

@@ -30,6 +30,7 @@ use jj_lib::revset::{
     RevsetEvaluationError, RevsetParseError, RevsetParseErrorKind, RevsetResolutionError,
 };
 use jj_lib::signing::SignInitError;
+use jj_lib::str_util::StringPatternParseError;
 use jj_lib::working_copy::{ResetError, SnapshotError, WorkingCopyStateError};
 use jj_lib::workspace::WorkspaceInitError;
 use thiserror::Error;
@@ -423,6 +424,9 @@ impl From<RevsetParseError> for CommandError {
                 name: _,
                 candidates,
             } => format_similarity_hint(candidates),
+            RevsetParseErrorKind::InvalidFunctionArguments { .. } => {
+                find_source_parse_error_hint(bottom_err)
+            }
             _ => None,
         };
         let mut cmd_err =
@@ -470,6 +474,8 @@ impl From<TemplateParseError> for CommandError {
             | TemplateParseErrorKind::NoSuchMethod { candidates, .. } => {
                 format_similarity_hint(candidates)
             }
+            TemplateParseErrorKind::InvalidArguments { .. }
+            | TemplateParseErrorKind::Expression(_) => find_source_parse_error_hint(bottom_err),
             _ => None,
         };
         let mut cmd_err =
@@ -489,7 +495,10 @@ impl From<FsPathParseError> for CommandError {
 
 impl From<clap::Error> for CommandError {
     fn from(err: clap::Error) -> Self {
-        cli_error(err)
+        let hint = find_source_parse_error_hint(&err);
+        let mut cmd_err = cli_error(err);
+        cmd_err.extend_hints(hint);
+        cmd_err
     }
 }
 
@@ -511,6 +520,24 @@ impl From<GitIgnoreError> for CommandError {
     }
 }
 
+fn find_source_parse_error_hint(err: &dyn error::Error) -> Option<String> {
+    let source = err.source()?;
+    if let Some(source) = source.downcast_ref() {
+        string_pattern_parse_error_hint(source)
+    } else {
+        None
+    }
+}
+
+fn string_pattern_parse_error_hint(err: &StringPatternParseError) -> Option<String> {
+    match err {
+        StringPatternParseError::InvalidKind(_) => {
+            Some("Try prefixing with one of `exact:`, `glob:` or `substring:`".into())
+        }
+        StringPatternParseError::GlobPattern(_) => None,
+    }
+}
+
 const BROKEN_PIPE_EXIT_CODE: u8 = 3;
 
 pub(crate) fn handle_command_result(ui: &mut Ui, result: Result<(), CommandError>) -> ExitCode {

cli/tests/test_branch_command.rs

@@ -396,9 +396,10 @@ fn test_branch_delete_glob() {
     // Unknown pattern kind
     let stderr = test_env.jj_cmd_cli_error(&repo_path, &["branch", "forget", "whatever:branch"]);
     insta::assert_snapshot!(stderr, @r###"
-    error: invalid value 'whatever:branch' for '[NAMES]...': Invalid string pattern kind "whatever:", try prefixing with one of `exact:`, `glob:` or `substring:`
+    error: invalid value 'whatever:branch' for '[NAMES]...': Invalid string pattern kind "whatever:"
 
     For more information, try '--help'.
+    Hint: Try prefixing with one of `exact:`, `glob:` or `substring:`
     "###);
 }
 

cli/tests/test_revset_output.rs

@@ -175,7 +175,8 @@ fn test_bad_function_call() {
       |          ^---------^
       |
       = Function "branches": Invalid string pattern
-    2: Invalid string pattern kind "bad:", try prefixing with one of `exact:`, `glob:` or `substring:`
+    2: Invalid string pattern kind "bad:"
+    Hint: Try prefixing with one of `exact:`, `glob:` or `substring:`
     "###);
 
     let stderr = test_env.jj_cmd_failure(&repo_path, &["log", "-r", "root()::whatever()"]);

lib/src/str_util.rs

@@ -25,7 +25,7 @@ use thiserror::Error;
 #[derive(Debug, Error)]
 pub enum StringPatternParseError {
     /// Unknown pattern kind is specified.
-    #[error(r#"Invalid string pattern kind "{0}:", try prefixing with one of `exact:`, `glob:` or `substring:`"#)]
+    #[error(r#"Invalid string pattern kind "{0}:""#)]
     InvalidKind(String),
     /// Failed to parse glob pattern.
     #[error(transparent)]