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diff --git a/lib/filevercmp.h b/lib/filevercmp.h
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+/* Compare file names containing version numbers.
+
+   Copyright (C) 1995 Ian Jackson <iwj10@cus.cam.ac.uk>
+   Copyright (C) 2001 Anthony Towns <aj@azure.humbug.org.au>
+   Copyright (C) 2008-2023 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation, either version 3 of the
+   License, or (at your option) any later version.
+
+   This file is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef FILEVERCMP_H
+#define FILEVERCMP_H
+
+/* This file uses _GL_ATTRIBUTE_PURE.  */
+#if !_GL_CONFIG_H_INCLUDED
+ #error "Please include config.h first."
+#endif
+
+#include <stddef.h>
+
+/* Compare strings A and B as file names containing version numbers,
+   and return an integer that is negative, zero, or positive depending
+   on whether A compares less than, equal to, or greater than B.
+
+   Use the following version sort algorithm:
+
+     1. Compare the strings' maximal-length non-digit prefixes lexically.
+        If there is a difference return that difference.
+        Otherwise discard the prefixes and continue with the next step.
+
+     2. Compare the strings' maximal-length digit prefixes, using
+        numeric comparison of the numbers represented by each prefix.
+        (Treat an empty prefix as zero; this can happen only at string end.)
+        If there is a difference, return that difference.
+        Otherwise discard the prefixes and continue with the next step.
+
+     3. If both strings are empty, return 0.  Otherwise continue with step 1.
+
+   In version sort, lexical comparison is left to right, byte by byte,
+   using the byte's numeric value (0-255), except that:
+
+     1. ASCII letters sort before other bytes.
+     2. A tilde sorts before anything, even an empty string.
+
+   In addition to the version sort rules, the following strings have
+   special priority and sort before all other strings (listed in order):
+
+     1. The empty string.
+     2. ".".
+     3. "..".
+     4. Strings starting with "." sort before other strings.
+
+   Before comparing two strings where both begin with non-".",
+   or where both begin with "." but neither is "." or "..",
+   suffixes matching the C-locale extended regular expression
+   (\.[A-Za-z~][A-Za-z0-9~]*)*$ are removed and the strings compared
+   without them, using version sort without special priority;
+   if they do not compare equal, this comparison result is used and
+   the suffixes are effectively ignored.  Otherwise, the entire
+   strings are compared using version sort.  When removing a suffix
+   from a nonempty string, remove the maximal-length suffix such that
+   the remaining string is nonempty.
+
+   This function is intended to be a replacement for strverscmp.  */
+int filevercmp (char const *a, char const *b) _GL_ATTRIBUTE_PURE;
+
+/* Like filevercmp, except compare the byte arrays A (of length ALEN)
+   and B (of length BLEN) so that A and B can contain '\0', which
+   sorts just before '\1'.  But if ALEN is -1 treat A as a string
+   terminated by '\0', and similarly for BLEN.  */
+int filenvercmp (char const *a, ptrdiff_t alen, char const *b, ptrdiff_t blen)
+  _GL_ATTRIBUTE_PURE;
+
+#endif /* FILEVERCMP_H */