Merge from gnulib

This incorporates:
2017-05-01 New module 'localtime-buffer'
2017-04-30 utimens: Add support for native Windows
* admin/merge-gnulib (AVOIDED_MODULES): Add tzset.
* configure.ac (tzset): No need for Emacs itself to check now.
* lib/gettimeofday.c, lib/time.in.h, lib/time_rz.c, lib/utimens.c:
* m4/gettimeofday.m4, m4/time_h.m4, m4/time_rz.m4: Copy from gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib/localtime-buffer.c, lib/localtime-buffer.h:
* m4/localtime-buffer.m4: New files, copied from gnulib.
* src/editfns.c (init_editfns): Assume tzset is callable.

7 files changed, 214 insertions, 75 deletions

diff --git a/lib/gettimeofday.c b/lib/gettimeofday.c
index 86f1a8c1d28..1039f77d182 100644
--- a/lib/gettimeofday.c
+++ b/lib/gettimeofday.c
@@ -29,72 +29,7 @@
 # include <windows.h>
 #endif
 
-#if GETTIMEOFDAY_CLOBBERS_LOCALTIME || TZSET_CLOBBERS_LOCALTIME
-
-/* Work around the bug in some systems whereby gettimeofday clobbers
-   the static buffer that localtime uses for its return value.  The
-   gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
-   this problem.  The tzset replacement is necessary for at least
-   Solaris 2.5, 2.5.1, and 2.6.  */
-
-static struct tm tm_zero_buffer;
-static struct tm *localtime_buffer_addr = &tm_zero_buffer;
-
-# undef localtime
-extern struct tm *localtime (time_t const *);
-
-# undef gmtime
-extern struct tm *gmtime (time_t const *);
-
-/* This is a wrapper for localtime.  It is used only on systems for which
-   gettimeofday clobbers the static buffer used for localtime's result.
-
-   On the first call, record the address of the static buffer that
-   localtime uses for its result.  */
-
-struct tm *
-rpl_localtime (time_t const *timep)
-{
-  struct tm *tm = localtime (timep);
-
-  if (localtime_buffer_addr == &tm_zero_buffer)
-    localtime_buffer_addr = tm;
-
-  return tm;
-}
-
-/* Same as above, since gmtime and localtime use the same buffer.  */
-struct tm *
-rpl_gmtime (time_t const *timep)
-{
-  struct tm *tm = gmtime (timep);
-
-  if (localtime_buffer_addr == &tm_zero_buffer)
-    localtime_buffer_addr = tm;
-
-  return tm;
-}
-
-#endif /* GETTIMEOFDAY_CLOBBERS_LOCALTIME || TZSET_CLOBBERS_LOCALTIME */
-
-#if TZSET_CLOBBERS_LOCALTIME
-
-# undef tzset
-extern void tzset (void);
-
-/* This is a wrapper for tzset, for systems on which tzset may clobber
-   the static buffer used for localtime's result.  */
-void
-rpl_tzset (void)
-{
-  /* Save and restore the contents of the buffer used for localtime's
-     result around the call to tzset.  */
-  struct tm save = *localtime_buffer_addr;
-  tzset ();
-  *localtime_buffer_addr = save;
-}
-
-#endif
+#include "localtime-buffer.h"
 
 #ifdef WINDOWS_NATIVE
 
@@ -119,7 +54,11 @@ initialize (void)
 
 /* This is a wrapper for gettimeofday.  It is used only on systems
    that lack this function, or whose implementation of this function
-   causes problems.  */
+   causes problems.
+   Work around the bug in some systems whereby gettimeofday clobbers
+   the static buffer that localtime uses for its return value.  The
+   gettimeofday function from Mac OS X 10.0.4 (i.e., Darwin 1.3.7) has
+   this problem.  */
 
 int
 gettimeofday (struct timeval *restrict tv, void *restrict tz)
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 59cdbdb847a..51ae1891244 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stat --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --avoid=utime-h --gnu-make --makefile-name=gnulib.mk.in --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub update-copyright utimens vla warnings
+# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stat --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=tzset --avoid=unsetenv --avoid=utime --avoid=utime-h --gnu-make --makefile-name=gnulib.mk.in --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub update-copyright utimens vla warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
@@ -307,6 +307,7 @@ GNULIB_TIME_R = @GNULIB_TIME_R@
 GNULIB_TIME_RZ = @GNULIB_TIME_RZ@
 GNULIB_TMPFILE = @GNULIB_TMPFILE@
 GNULIB_TTYNAME_R = @GNULIB_TTYNAME_R@
+GNULIB_TZSET = @GNULIB_TZSET@
 GNULIB_UNISTD_H_NONBLOCKING = @GNULIB_UNISTD_H_NONBLOCKING@
 GNULIB_UNISTD_H_SIGPIPE = @GNULIB_UNISTD_H_SIGPIPE@
 GNULIB_UNLINK = @GNULIB_UNLINK@
@@ -504,6 +505,7 @@ HAVE_SYS_TYPES_H = @HAVE_SYS_TYPES_H@
 HAVE_TIMEGM = @HAVE_TIMEGM@
 HAVE_TIMEZONE_T = @HAVE_TIMEZONE_T@
 HAVE_TYPE_VOLATILE_SIG_ATOMIC_T = @HAVE_TYPE_VOLATILE_SIG_ATOMIC_T@
+HAVE_TZSET = @HAVE_TZSET@
 HAVE_UNISTD_H = @HAVE_UNISTD_H@
 HAVE_UNLINKAT = @HAVE_UNLINKAT@
 HAVE_UNLOCKPT = @HAVE_UNLOCKPT@
@@ -780,6 +782,7 @@ REPLACE_SYMLINKAT = @REPLACE_SYMLINKAT@
 REPLACE_TIMEGM = @REPLACE_TIMEGM@
 REPLACE_TMPFILE = @REPLACE_TMPFILE@
 REPLACE_TTYNAME_R = @REPLACE_TTYNAME_R@
+REPLACE_TZSET = @REPLACE_TZSET@
 REPLACE_UNLINK = @REPLACE_UNLINK@
 REPLACE_UNLINKAT = @REPLACE_UNLINKAT@
 REPLACE_UNSETENV = @REPLACE_UNSETENV@
@@ -879,6 +882,7 @@ gamedir = @gamedir@
 gamegroup = @gamegroup@
 gameuser = @gameuser@
 gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7 = @gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7@
+gl_GNULIB_ENABLED_2049e887c7e5308faad27b3f894bb8c9 = @gl_GNULIB_ENABLED_2049e887c7e5308faad27b3f894bb8c9@
 gl_GNULIB_ENABLED_260941c0e5dc67ec9e87d1fb321c300b = @gl_GNULIB_ENABLED_260941c0e5dc67ec9e87d1fb321c300b@
 gl_GNULIB_ENABLED_5264294aa0a5557541b53c8c741f7f31 = @gl_GNULIB_ENABLED_5264294aa0a5557541b53c8c741f7f31@
 gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c = @gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c@
@@ -1700,6 +1704,19 @@ EXTRA_DIST += limits.in.h
 endif
 ## end   gnulib module limits-h
 
+## begin gnulib module localtime-buffer
+ifeq (,$(OMIT_GNULIB_MODULE_localtime-buffer))
+
+ifneq (,$(gl_GNULIB_ENABLED_2049e887c7e5308faad27b3f894bb8c9))
+
+endif
+EXTRA_DIST += localtime-buffer.c localtime-buffer.h
+
+EXTRA_libgnu_a_SOURCES += localtime-buffer.c
+
+endif
+## end   gnulib module localtime-buffer
+
 ## begin gnulib module lstat
 ifeq (,$(OMIT_GNULIB_MODULE_lstat))
 
@@ -2707,7 +2724,6 @@ time.h: time.in.h $(top_builddir)/config.status $(CXXDEFS_H) $(ARG_NONNULL_H) $(
               -e 's|@''PRAGMA_COLUMNS''@|@PRAGMA_COLUMNS@|g' \
               -e 's|@''NEXT_TIME_H''@|$(NEXT_TIME_H)|g' \
               -e 's/@''GNULIB_CTIME''@/$(GNULIB_CTIME)/g' \
-              -e 's/@''GNULIB_GETTIMEOFDAY''@/$(GNULIB_GETTIMEOFDAY)/g' \
               -e 's/@''GNULIB_LOCALTIME''@/$(GNULIB_LOCALTIME)/g' \
               -e 's/@''GNULIB_MKTIME''@/$(GNULIB_MKTIME)/g' \
               -e 's/@''GNULIB_NANOSLEEP''@/$(GNULIB_NANOSLEEP)/g' \
@@ -2716,11 +2732,13 @@ time.h: time.in.h $(top_builddir)/config.status $(CXXDEFS_H) $(ARG_NONNULL_H) $(
               -e 's/@''GNULIB_TIMEGM''@/$(GNULIB_TIMEGM)/g' \
               -e 's/@''GNULIB_TIME_R''@/$(GNULIB_TIME_R)/g' \
               -e 's/@''GNULIB_TIME_RZ''@/$(GNULIB_TIME_RZ)/g' \
+              -e 's/@''GNULIB_TZSET''@/$(GNULIB_TZSET)/g' \
               -e 's|@''HAVE_DECL_LOCALTIME_R''@|$(HAVE_DECL_LOCALTIME_R)|g' \
               -e 's|@''HAVE_NANOSLEEP''@|$(HAVE_NANOSLEEP)|g' \
               -e 's|@''HAVE_STRPTIME''@|$(HAVE_STRPTIME)|g' \
               -e 's|@''HAVE_TIMEGM''@|$(HAVE_TIMEGM)|g' \
               -e 's|@''HAVE_TIMEZONE_T''@|$(HAVE_TIMEZONE_T)|g' \
+              -e 's|@''HAVE_TZSET''@|$(HAVE_TZSET)|g' \
               -e 's|@''REPLACE_CTIME''@|$(REPLACE_CTIME)|g' \
               -e 's|@''REPLACE_GMTIME''@|$(REPLACE_GMTIME)|g' \
               -e 's|@''REPLACE_LOCALTIME''@|$(REPLACE_LOCALTIME)|g' \
@@ -2729,6 +2747,7 @@ time.h: time.in.h $(top_builddir)/config.status $(CXXDEFS_H) $(ARG_NONNULL_H) $(
               -e 's|@''REPLACE_NANOSLEEP''@|$(REPLACE_NANOSLEEP)|g' \
               -e 's|@''REPLACE_STRFTIME''@|$(REPLACE_STRFTIME)|g' \
               -e 's|@''REPLACE_TIMEGM''@|$(REPLACE_TIMEGM)|g' \
+              -e 's|@''REPLACE_TZSET''@|$(REPLACE_TZSET)|g' \
               -e 's|@''PTHREAD_H_DEFINES_STRUCT_TIMESPEC''@|$(PTHREAD_H_DEFINES_STRUCT_TIMESPEC)|g' \
               -e 's|@''SYS_TIME_H_DEFINES_STRUCT_TIMESPEC''@|$(SYS_TIME_H_DEFINES_STRUCT_TIMESPEC)|g' \
               -e 's|@''TIME_H_DEFINES_STRUCT_TIMESPEC''@|$(TIME_H_DEFINES_STRUCT_TIMESPEC)|g' \
diff --git a/lib/localtime-buffer.c b/lib/localtime-buffer.c
new file mode 100644
index 00000000000..f84ad3e8238
--- /dev/null
+++ b/lib/localtime-buffer.c
@@ -0,0 +1,58 @@
+/* Provide access to the last buffer returned by localtime() or gmtime().
+
+   Copyright (C) 2001-2003, 2005-2007, 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/>.  */
+
+/* written by Jim Meyering */
+
+#include <config.h>
+
+/* Specification.  */
+#include "localtime-buffer.h"
+
+#if GETTIMEOFDAY_CLOBBERS_LOCALTIME || TZSET_CLOBBERS_LOCALTIME
+
+static struct tm tm_zero_buffer;
+struct tm *localtime_buffer_addr = &tm_zero_buffer;
+
+/* This is a wrapper for localtime.
+
+   On the first call, record the address of the static buffer that
+   localtime uses for its result.  */
+
+struct tm *
+rpl_localtime (time_t const *timep)
+{
+  struct tm *tm = localtime (timep);
+
+  if (localtime_buffer_addr == &tm_zero_buffer)
+    localtime_buffer_addr = tm;
+
+  return tm;
+}
+
+/* Same as above, since gmtime and localtime use the same buffer.  */
+struct tm *
+rpl_gmtime (time_t const *timep)
+{
+  struct tm *tm = gmtime (timep);
+
+  if (localtime_buffer_addr == &tm_zero_buffer)
+    localtime_buffer_addr = tm;
+
+  return tm;
+}
+
+#endif
diff --git a/lib/localtime-buffer.h b/lib/localtime-buffer.h
new file mode 100644
index 00000000000..483a579bda4
--- /dev/null
+++ b/lib/localtime-buffer.h
@@ -0,0 +1,27 @@
+/* Provide access to the last buffer returned by localtime() or gmtime().
+
+   Copyright (C) 2001-2003, 2005-2007, 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/>.  */
+
+/* written by Jim Meyering */
+
+#include <time.h>
+
+#if GETTIMEOFDAY_CLOBBERS_LOCALTIME || TZSET_CLOBBERS_LOCALTIME
+
+/* The address of the last buffer returned by localtime() or gmtime().  */
+extern struct tm *localtime_buffer_addr;
+
+#endif
diff --git a/lib/time.in.h b/lib/time.in.h
index d2a0302f464..f0c7ef86667 100644
--- a/lib/time.in.h
+++ b/lib/time.in.h
@@ -120,6 +120,24 @@ _GL_CXXALIAS_SYS (nanosleep, int,
 _GL_CXXALIASWARN (nanosleep);
 # endif
 
+/* Initialize time conversion information.  */
+# if @GNULIB_TZSET@
+#  if @REPLACE_TZSET@
+#   if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#    undef tzset
+#    define tzset rpl_tzset
+#   endif
+_GL_FUNCDECL_RPL (tzset, void, (void));
+_GL_CXXALIAS_RPL (tzset, void, (void));
+#  else
+#   if ! @HAVE_TZSET@
+_GL_FUNCDECL_SYS (tzset, void, (void));
+#   endif
+_GL_CXXALIAS_SYS (tzset, void, (void));
+#  endif
+_GL_CXXALIASWARN (tzset);
+# endif
+
 /* Return the 'time_t' representation of TP and normalize TP.  */
 # if @GNULIB_MKTIME@
 #  if @REPLACE_MKTIME@
@@ -187,7 +205,7 @@ _GL_CXXALIASWARN (gmtime_r);
 /* Convert TIMER to RESULT, assuming local time and UTC respectively.  See
    <http://www.opengroup.org/susv3xsh/localtime.html> and
    <http://www.opengroup.org/susv3xsh/gmtime.html>.  */
-# if @GNULIB_LOCALTIME@ || @GNULIB_GETTIMEOFDAY@
+# if @GNULIB_LOCALTIME@ || @REPLACE_LOCALTIME@
 #  if @REPLACE_LOCALTIME@
 #   if !(defined __cplusplus && defined GNULIB_NAMESPACE)
 #    undef localtime
@@ -202,7 +220,7 @@ _GL_CXXALIAS_SYS (localtime, struct tm *, (time_t const *__timer));
 _GL_CXXALIASWARN (localtime);
 # endif
 
-# if @GNULIB_GETTIMEOFDAY@
+# if 0 || @REPLACE_GMTIME@
 #  if @REPLACE_GMTIME@
 #   if !(defined __cplusplus && defined GNULIB_NAMESPACE)
 #    undef gmtime
diff --git a/lib/time_rz.c b/lib/time_rz.c
index c41a8ef47ac..17bc11c20e9 100644
--- a/lib/time_rz.c
+++ b/lib/time_rz.c
@@ -40,10 +40,6 @@
 # define SIZE_MAX ((size_t) -1)
 #endif
 
-#if !HAVE_TZSET
-static void tzset (void) { }
-#endif
-
 /* The approximate size to use for small allocation requests.  This is
    the largest "small" request for the GNU C library malloc.  */
 enum { DEFAULT_MXFAST = 64 * sizeof (size_t) / 4 };
diff --git a/lib/utimens.c b/lib/utimens.c
index 3b451193350..0b3b8e2f3af 100644
--- a/lib/utimens.c
+++ b/lib/utimens.c
@@ -35,6 +35,12 @@
 #include "stat-time.h"
 #include "timespec.h"
 
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+# define WIN32_LEAN_AND_MEAN
+# include <windows.h>
+# include "msvc-nothrow.h"
+#endif
+
 /* Avoid recursion with rpl_futimens or rpl_utimensat.  */
 #undef futimens
 #undef utimensat
@@ -271,6 +277,82 @@ fdutimens (int fd, char const *file, struct timespec const timespec[2])
   lutimensat_works_really = -1;
 #endif /* HAVE_UTIMENSAT || HAVE_FUTIMENS */
 
+#if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+  /* On native Windows, use SetFileTime(). See
+     <https://msdn.microsoft.com/en-us/library/ms724933.aspx>
+     <https://msdn.microsoft.com/en-us/library/ms724284.aspx>  */
+  if (0 <= fd)
+    {
+      HANDLE handle;
+      FILETIME current_time;
+      FILETIME last_access_time;
+      FILETIME last_write_time;
+
+      handle = (HANDLE) _get_osfhandle (fd);
+      if (handle == INVALID_HANDLE_VALUE)
+        {
+          errno = EBADF;
+          return -1;
+        }
+
+      if (ts == NULL || ts[0].tv_nsec == UTIME_NOW || ts[1].tv_nsec == UTIME_NOW)
+        {
+          /* GetSystemTimeAsFileTime
+             <https://msdn.microsoft.com/en-us/library/ms724397.aspx>.
+             It would be overkill to use
+             GetSystemTimePreciseAsFileTime
+             <https://msdn.microsoft.com/en-us/library/hh706895.aspx>.  */
+          GetSystemTimeAsFileTime (&current_time);
+        }
+
+      if (ts == NULL || ts[0].tv_nsec == UTIME_NOW)
+        {
+          last_access_time = current_time;
+        }
+      else if (ts[0].tv_nsec == UTIME_OMIT)
+        {
+          last_access_time.dwLowDateTime = 0;
+          last_access_time.dwHighDateTime = 0;
+        }
+      else
+        {
+          ULONGLONG time_since_16010101 =
+            (ULONGLONG) ts[0].tv_sec * 10000000 + ts[0].tv_nsec / 100 + 116444736000000000LL;
+          last_access_time.dwLowDateTime = (DWORD) time_since_16010101;
+          last_access_time.dwHighDateTime = time_since_16010101 >> 32;
+        }
+
+      if (ts == NULL || ts[1].tv_nsec == UTIME_NOW)
+        {
+          last_write_time = current_time;
+        }
+      else if (ts[1].tv_nsec == UTIME_OMIT)
+        {
+          last_write_time.dwLowDateTime = 0;
+          last_write_time.dwHighDateTime = 0;
+        }
+      else
+        {
+          ULONGLONG time_since_16010101 =
+            (ULONGLONG) ts[1].tv_sec * 10000000 + ts[1].tv_nsec / 100 + 116444736000000000LL;
+          last_write_time.dwLowDateTime = (DWORD) time_since_16010101;
+          last_write_time.dwHighDateTime = time_since_16010101 >> 32;
+        }
+
+      if (SetFileTime (handle, NULL, &last_access_time, &last_write_time))
+        return 0;
+      else
+        {
+          #if 0
+          DWORD sft_error = GetLastError ();
+          fprintf (stderr, "utime SetFileTime error 0x%x\n", (unsigned int) sft_error);
+          #endif
+          errno = EINVAL;
+          return -1;
+        }
+    }
+#endif
+
   /* The platform lacks an interface to set file timestamps with
      nanosecond resolution, so do the best we can, discarding any
      fractional part of the timestamp.  */