Add command to replace buffer contents

Add a new command 'replace-buffer-contents' that uses the Myers diff
algorithm to non-destructively replace the accessible portion of the
current buffer.  The Myers algorithm is implemented in Gnulib.

* src/editfns.c (Freplace_buffer_contents): New command.
(set_bit, bit_is_set, buffer_chars_equal): New helper functions.
(syms_of_editfns): Define new command.

* test/src/editfns-tests.el (replace-buffer-contents-1)
(replace-buffer-contents-2): New unit tests.

* src/buffer.h (BUF_FETCH_CHAR_AS_MULTIBYTE): New helper macro.

* admin/merge-gnulib (GNULIB_MODULES): Add diffseq.h and minmax.h.

1 files changed, 60 insertions, 0 deletions

diff --git a/lib/minmax.h b/lib/minmax.h
new file mode 100644
index 00000000000..6b602a94fdb
--- /dev/null
+++ b/lib/minmax.h
@@ -0,0 +1,60 @@
+/* MIN, MAX macros.
+   Copyright (C) 1995, 1998, 2001, 2003, 2005, 2009-2017 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, 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 _MINMAX_H
+#define _MINMAX_H
+
+/* Note: MIN, MAX are also defined in <sys/param.h> on some systems
+   (glibc, IRIX, HP-UX, OSF/1).  Therefore you might get warnings about
+   MIN, MAX macro redefinitions on some systems; the workaround is to
+   #include this file as the last one among the #include list.  */
+
+/* Before we define the following symbols we get the <limits.h> file
+   since otherwise we get redefinitions on some systems if <limits.h> is
+   included after this file.  Likewise for <sys/param.h>.
+   If more than one of these system headers define MIN and MAX, pick just
+   one of the headers (because the definitions most likely are the same).  */
+#if HAVE_MINMAX_IN_LIMITS_H
+# include <limits.h>
+#elif HAVE_MINMAX_IN_SYS_PARAM_H
+# include <sys/param.h>
+#endif
+
+/* Note: MIN and MAX should be used with two arguments of the
+   same type.  They might not return the minimum and maximum of their two
+   arguments, if the arguments have different types or have unusual
+   floating-point values.  For example, on a typical host with 32-bit 'int',
+   64-bit 'long long', and 64-bit IEEE 754 'double' types:
+
+     MAX (-1, 2147483648) returns 4294967295.
+     MAX (9007199254740992.0, 9007199254740993) returns 9007199254740992.0.
+     MAX (NaN, 0.0) returns 0.0.
+     MAX (+0.0, -0.0) returns -0.0.
+
+   and in each case the answer is in some sense bogus.  */
+
+/* MAX(a,b) returns the maximum of A and B.  */
+#ifndef MAX
+# define MAX(a,b) ((a) > (b) ? (a) : (b))
+#endif
+
+/* MIN(a,b) returns the minimum of A and B.  */
+#ifndef MIN
+# define MIN(a,b) ((a) < (b) ? (a) : (b))
+#endif
+
+#endif /* _MINMAX_H */