switch to freebsd implementations of strftime and strptime

This allows the tools to have less deficient behavior on musl,
as freebsd implements tons of extensions that musl does not, which
regularly breaks scripts even in projects that have explicit
support for BSD date, while also making them less useful.

import-src.sh

@@ -234,6 +234,8 @@ cp -p usr/src/lib/libopenbsd/ohash.c ${CWD}/src.orig/compat
 cp -p usr/src/lib/libc/gen/setmode.c ${CWD}/src.orig/compat
 cp -p usr/src/lib/libc/string/strmode.c ${CWD}/src.orig/compat
 cp -p usr/src/lib/libc/gen/stringlist.c ${CWD}/src.orig/compat
+cp -p usr/src/lib/libc/stdtime/strptime.c ${CWD}/src.orig/compat
+cp -p usr/src/lib/libc/stdtime/strftime.c ${CWD}/src.orig/compat
 cp -p usr/src/contrib/libc-vis/vis.c ${CWD}/src.orig/compat
 cp -p usr/src/include/stringlist.h ${CWD}/src.orig/include
 cp -p usr/src/contrib/libc-vis/vis.h ${CWD}/src.orig/include

include/time_bsd.h

@@ -0,0 +1,42 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2023 Daniel Kolesa
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef TIME_BSD_H
+#define TIME_BSD_H
+
+#include <stddef.h>
+#include <time.h>
+
+/* FreeBSD implementations of strptime and strftime
+ *
+ * used to get consistent behavior of utilities like date(1) even on libcs
+ * that do not bother to implement the various extensions such as %s
+ */
+char *strptime_bsd(const char *__restrict buf, const char *__restrict fmt, struct tm *__restrict tm);
+size_t strftime_bsd(char *__restrict s, size_t maxsize, const char *__restrict format, const struct tm *__restrict t);
+
+#endif