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.

2 files changed, 50 insertions, 0 deletions

diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 8f53a990e34..1ac58e871cc 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -61,6 +61,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module crypto/sha1:
   # Code from module crypto/sha256:
   # Code from module crypto/sha512:
+  # Code from module diffseq:
   # Code from module dirent:
   # Code from module dirfd:
   # Code from module dosname:
@@ -105,6 +106,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module lstat:
   # Code from module manywarnings:
   # Code from module memrchr:
+  # Code from module minmax:
   # Code from module mkostemp:
   # Code from module mktime:
   # Code from module mktime-internal:
@@ -289,6 +291,7 @@ AC_DEFUN([gl_INIT],
     gl_PREREQ_MEMRCHR
   fi
   gl_STRING_MODULE_INDICATOR([memrchr])
+  gl_MINMAX
   gl_FUNC_MKOSTEMP
   if test $HAVE_MKOSTEMP = 0; then
     AC_LIBOBJ([mkostemp])
@@ -821,6 +824,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/count-one-bits.h
   lib/count-trailing-zeros.c
   lib/count-trailing-zeros.h
+  lib/diffseq.h
   lib/dirent.in.h
   lib/dirfd.c
   lib/dosname.h
@@ -875,6 +879,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/md5.c
   lib/md5.h
   lib/memrchr.c
+  lib/minmax.h
   lib/mkostemp.c
   lib/mktime-internal.h
   lib/mktime.c
@@ -991,6 +996,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/manywarnings.m4
   m4/md5.m4
   m4/memrchr.m4
+  m4/minmax.m4
   m4/mkostemp.m4
   m4/mktime.m4
   m4/multiarch.m4
diff --git a/m4/minmax.m4 b/m4/minmax.m4
new file mode 100644
index 00000000000..6845fce89c4
--- /dev/null
+++ b/m4/minmax.m4
@@ -0,0 +1,44 @@
+# minmax.m4 serial 4
+dnl Copyright (C) 2005, 2009-2017 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_PREREQ([2.53])
+
+AC_DEFUN([gl_MINMAX],
+[
+  AC_REQUIRE([gl_PREREQ_MINMAX])
+])
+
+# Prerequisites of lib/minmax.h.
+AC_DEFUN([gl_PREREQ_MINMAX],
+[
+  gl_MINMAX_IN_HEADER([limits.h])
+  gl_MINMAX_IN_HEADER([sys/param.h])
+])
+
+dnl gl_MINMAX_IN_HEADER(HEADER)
+dnl The parameter has to be a literal header name; it cannot be macro,
+dnl nor a shell variable. (Because autoheader collects only AC_DEFINE
+dnl invocations with a literal macro name.)
+AC_DEFUN([gl_MINMAX_IN_HEADER],
+[
+  m4_pushdef([header], AS_TR_SH([$1]))
+  m4_pushdef([HEADER], AS_TR_CPP([$1]))
+  AC_CACHE_CHECK([whether <$1> defines MIN and MAX],
+    [gl_cv_minmax_in_]header,
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <$1>
+            int x = MIN (42, 17);]],
+          [[]])],
+       [gl_cv_minmax_in_]header[=yes],
+       [gl_cv_minmax_in_]header[=no])])
+  if test $gl_cv_minmax_in_[]header = yes; then
+    AC_DEFINE([HAVE_MINMAX_IN_]HEADER, 1,
+      [Define to 1 if <$1> defines the MIN and MAX macros.])
+  fi
+  m4_popdef([HEADER])
+  m4_popdef([header])
+])