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diff --git a/lib/filevercmp.h b/lib/filevercmp.h
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+/*
+   Copyright (C) 1995 Ian Jackson <iwj10@cus.cam.ac.uk>
+   Copyright (C) 2001 Anthony Towns <aj@azure.humbug.org.au>
+   Copyright (C) 2008-2016 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef FILEVERCMP_H
+#define FILEVERCMP_H
+
+/* Compare version strings:
+
+   This function compares strings S1 and S2:
+   1) By PREFIX in the same way as strcmp.
+   2) Then by VERSION (most similarly to version compare of Debian's dpkg).
+      Leading zeros in version numbers are ignored.
+   3) If both (PREFIX and  VERSION) are equal, strcmp function is used for
+      comparison. So this function can return 0 if (and only if) strings S1
+      and S2 are identical.
+
+   It returns number >0 for S1 > S2, 0 for S1 == S2 and number <0 for S1 < S2.
+
+   This function compares strings, in a way that if VER1 and VER2 are version
+   numbers and PREFIX and SUFFIX (SUFFIX defined as (\.[A-Za-z~][A-Za-z0-9~]*)*)
+   are strings then VER1 < VER2 implies filevercmp (PREFIX VER1 SUFFIX,
+   PREFIX VER2 SUFFIX) < 0.
+
+   This function is intended to be a replacement for strverscmp. */
+int filevercmp (const char *s1, const char *s2) _GL_ATTRIBUTE_PURE;
+
+#endif /* FILEVERCMP_H */