From 21709a58682b9fef53e3e3dec97a0fe4498334e3 Mon Sep 17 00:00:00 2001
From: Takashi Kokubun <takashikkbn@gmail.com>
Date: Fri, 12 Sep 2025 14:58:07 -0700
Subject: [PATCH] merge revision(s) 7a05dbc47831a655a1ef8a1635f88292acd325da:
 [Backport #21561]

	File.dirname: return consistent encoding for `"."`

	[Bug #21561]

	It's preferable if the method is consistent in the encoding in
	the returned string.
---
 file.c    | 7 +++++--
 version.h | 2 +-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/file.c b/file.c
index 585dd90665..414479fae4 100644
--- a/file.c
+++ b/file.c
@@ -4947,8 +4947,11 @@ rb_file_dirname_n(VALUE fname, int n)
             break;
         }
     }
-    if (p == name)
-        return rb_usascii_str_new2(".");
+    if (p == name) {
+        dirname = rb_str_new(".", 1);
+        rb_enc_copy(dirname, fname);
+        return dirname;
+    }
 #ifdef DOSISH_DRIVE_LETTER
     if (has_drive_letter(name) && isdirsep(*(name + 2))) {
         const char *top = skiproot(name + 2, end, enc);
diff --git a/version.h b/version.h
index 631d03013b..66b6b78882 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 5
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 53
+#define RUBY_PATCHLEVEL 54
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"