ls: add --quoting-style=locale support

Implement locale-aware quoting for the ls command, allowing filenames
to be quoted using locale-specific quotation marks based on the
current LC_CTYPE setting.

Features:
- Add Quotes::Locale variant for locale-aware quoting
- Create locale_quotes module with comprehensive locale mappings
- Support 20+ languages with appropriate quote characters:
  * Romance languages (French, Spanish, etc.): guillemets
  * Germanic languages (German, Czech, etc.): low-9 and high quotes
  * Japanese: corner brackets
  * Chinese/Korean: CJK curly quotes
  * English/default: ASCII double quotes
- Proper UTF-8 handling for multi-byte quote characters
- Environment variable precedence: LC_ALL > LC_CTYPE > LANG
- Localized help text in English and French

Implementation:
- Enhanced CQuoter to dynamically detect and apply locale quotes
- Added --quoting-style=locale CLI option
- Follows C-style quoting semantics (always-quote behavior)
- Safe fallback to ASCII double quotes for unknown locales
- Added spell-checker:ignore comments for technical terms

Testing:
- Verified with multiple locales (en_US, fr_FR, de_DE, ja_JP, zh_CN)
- All existing tests pass
- Help text properly localized

test(ls): add comprehensive tests for --quoting-style=locale

Add test coverage for locale-aware quoting functionality:
- Tests 10 different locales with appropriate quotation marks
- Verifies English, French, German, Japanese, Chinese, Russian, Spanish, Polish, C, and POSIX locales
- Tests escape sequence handling with locale quoting (newline character)
- Validates UTF-8 encoding of multi-byte quote characters

test(ls): use only CI-available locales in locale quoting test

Fix test failures by limiting locale tests to those available in the CI environment.
CI only generates en_US.UTF-8, fr_FR.UTF-8, es_ES.UTF-8, and sv_SE.UTF-8.

Removed tests for: de_DE, ja_JP, zh_CN, pl_PL, ru_RU.UTF-8
- These locales are not generated in .github/workflows/GnuTests.yml
- The locale_quotes module unit tests still validate these quote types
- This keeps the integration test CI-friendly while maintaining comprehensive coverage

test(ls): add missing tests for locale quoting feature

Add missing Quotes::Locale test case in test_quotes_display() to ensure
the Display trait implementation is tested for all quote variants.

Add comprehensive unit tests for locale_quotes module:
- Test locale environment variable precedence (LC_ALL > LC_CTYPE > LANG)
- Validate quote character mappings for all supported locales
- Ensure Romance, Germanic, Slavic, and Asian language quotes work correctly
- Test locale string parsing with encoding and modifiers
- Verify fallback behavior for unknown locales

This adds 17 unit tests covering the locale detection and quote mapping
functionality that was previously untested.

test(ls): add integration tests for locale quoting with environment variables

Add test_ls_quoting_style_locale_env_vars to verify that --quoting-style=locale
correctly responds to different locale environment variables (LC_ALL).

Tests verify:
- French locale (fr_FR.UTF-8) uses guillemets (« »)
- Spanish locale (es_ES.UTF-8) uses guillemets (« »)
- Swedish locale (sv_SE.UTF-8) uses ASCII quotes
- C locale uses ASCII quotes

Note: Environment variable precedence testing (LC_ALL > LC_CTYPE > LANG) is
already comprehensively covered in unit tests (locale_quotes.rs). These
integration tests focus on end-to-end functionality.

fix: address CI failures in locale quoting tests

- Add locale/typography terms (CTYPE, Guillemets, guillemets) to spell checker dictionary
- Skip newline filename test on Windows where such filenames are invalid

optimize locale quoting and clean up code

- Optimize locale parsing to avoid multiple string splits and allocations
- Use efficient find() operations instead of split() for locale parsing
- Remove redundant comments and GNU-specific references for MIT compliance
- Clean up documentation to include only essential API documentation
- Maintain all functionality while improving performance to fix CodSpeed regression

Author: naoNao89

.vscode/cspell.dictionaries/jargon.wordlist.txt

@@ -214,3 +214,8 @@ TUNABLES
 tunables
 VMULL
 vmull
+
+# * locale and typography
+CTYPE
+Guillemets
+guillemets

src/uu/ls/locales/en-US.ftl

@@ -45,6 +45,7 @@ ls-help-set-quoting-style = Set quoting style.
 ls-help-literal-quoting-style = Use literal quoting style. Equivalent to `--quoting-style=literal`
 ls-help-escape-quoting-style = Use escape quoting style. Equivalent to `--quoting-style=escape`
 ls-help-c-quoting-style = Use C quoting style. Equivalent to `--quoting-style=c`
+ls-help-locale-quoting-style = Use locale-aware quoting style. Uses quotation marks appropriate for the current locale (e.g., « » for French, „ " for German, 「 」 for Japanese). Equivalent to `--quoting-style=locale`
 ls-help-replace-control-chars = Replace control characters with '?' if they are not escaped.
 ls-help-show-control-chars = Show control characters 'as is' if they are not escaped.
 ls-help-show-time-field = Show time in <field>:

src/uu/ls/locales/fr-FR.ftl

@@ -45,6 +45,7 @@ ls-help-set-quoting-style = Définir le style de citation.
 ls-help-literal-quoting-style = Utiliser le style de citation littéral. Équivalent à `--quoting-style=literal`
 ls-help-escape-quoting-style = Utiliser le style de citation d'échappement. Équivalent à `--quoting-style=escape`
 ls-help-c-quoting-style = Utiliser le style de citation C. Équivalent à `--quoting-style=c`
+ls-help-locale-quoting-style = Utiliser le style de citation adapté à la locale. Utilise les guillemets appropriés à la locale actuelle (par ex., « » pour le français, „ " pour l'allemand, 「 」 pour le japonais). Équivalent à `--quoting-style=locale`
 ls-help-replace-control-chars = Remplacer les caractères de contrôle par '?' s'ils ne sont pas échappés.
 ls-help-show-control-chars = Afficher les caractères de contrôle 'tels quels' s'ils ne sont pas échappés.
 ls-help-show-time-field = Afficher l'heure dans <champ> :

src/uu/ls/src/ls.rs

@@ -664,6 +664,9 @@ fn match_quoting_style_name(style: &str, show_control: bool) -> Option<QuotingSt
         "shell-escape-always" => Some(QuotingStyle::SHELL_ESCAPE_QUOTE),
         "c" => Some(QuotingStyle::C_DOUBLE),
         "escape" => Some(QuotingStyle::C_NO_QUOTES),
+        "locale" => Some(QuotingStyle::C {
+            quotes: uucore::quoting_style::Quotes::Locale,
+        }),
         _ => None,
     }
     .map(|qs| qs.show_control(show_control))
@@ -1364,6 +1367,7 @@ pub fn uu_app() -> Command {
                 PossibleValue::new("shell-escape-always"),
                 PossibleValue::new("c").alias("c-maybe"),
                 PossibleValue::new("escape"),
+                PossibleValue::new("locale"),
             ]))
             .overrides_with_all([
                 QUOTING_STYLE,

src/uucore/src/lib/features/quoting_style/c_quoter.rs

@@ -3,12 +3,15 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-use super::{EscapedChar, Quoter, Quotes};
+use super::{EscapedChar, Quoter, Quotes, locale_quotes};
 
 pub(super) struct CQuoter {
     /// The type of quotes to use.
     quotes: Quotes,
 
+    /// Closing quote character (for Locale variant).
+    close_quote: char,
+
     dirname: bool,
 
     buffer: Vec<u8>,
@@ -17,18 +20,37 @@ pub(super) struct CQuoter {
 impl CQuoter {
     pub fn new(quotes: Quotes, dirname: bool, size_hint: usize) -> Self {
         let mut buffer = Vec::with_capacity(size_hint);
+
+        let (open_quote, close_quote) = match quotes {
+            Quotes::None => ('\0', '\0'),
+            Quotes::Single => ('\'', '\''),
+            Quotes::Double => ('"', '"'),
+            Quotes::Locale => locale_quotes::get_locale_quote_chars(),
+        };
+
+        // Add opening quote to buffer
         match quotes {
             Quotes::None => (),
-            Quotes::Single => buffer.push(b'\''),
-            Quotes::Double => buffer.push(b'"'),
+            Quotes::Single | Quotes::Double => buffer.push(open_quote as u8),
+            Quotes::Locale => Self::encode_quote_to_buffer(open_quote, &mut buffer),
         }
 
         Self {
             quotes,
+            close_quote,
             dirname,
             buffer,
         }
     }
+
+    /// Helper method to encode a quote character to the buffer.
+    ///
+    /// This handles UTF-8 encoding for locale-specific quote characters.
+    fn encode_quote_to_buffer(quote: char, buffer: &mut Vec<u8>) {
+        let mut buf = [0; 4];
+        let quote_str = quote.encode_utf8(&mut buf);
+        buffer.extend_from_slice(quote_str.as_bytes());
+    }
 }
 
 impl Quoter for CQuoter {
@@ -47,10 +69,11 @@ impl Quoter for CQuoter {
     }
 
     fn finalize(mut self: Box<Self>) -> Vec<u8> {
+        // Add closing quote to buffer
         match self.quotes {
             Quotes::None => (),
-            Quotes::Single => self.buffer.push(b'\''),
-            Quotes::Double => self.buffer.push(b'"'),
+            Quotes::Single | Quotes::Double => self.buffer.push(self.close_quote as u8),
+            Quotes::Locale => Self::encode_quote_to_buffer(self.close_quote, &mut self.buffer),
         }
         self.buffer
     }