tar: handle -m (--touch) switch, enabled by FEATURE_TAR_NOPRESERVE_TIME

function                                             old     new   delta
.rodata                                             2731    2779     +48
usage_messages                                       432     471     +39
tar_main                                             603     614     +11
tar_longopts                                         211     219      +8
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 106/0)             Total: 106 bytes

Signed-off-by: Mikhail Gusarov <dottedmag@dottedmag.net>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

archival/Config.in

@@ -276,6 +276,13 @@ config FEATURE_TAR_UNAME_GNAME
 	  listings (-t) and preserving permissions when unpacking (-p).
 	  +200 bytes.
 
+config FEATURE_TAR_NOPRESERVE_TIME
+	bool "Enable -m (do not preserve time) option"
+	default n
+	depends on TAR
+	help
+	  With this option busybox supports GNU tar -m (do not preserve time) option.
+
 endif #tar
 
 config UNCOMPRESS

archival/tar.c

@@ -748,6 +748,7 @@ enum {
 	IF_FEATURE_TAR_FROM(     OPTBIT_EXCLUDE_FROM,)
 	IF_FEATURE_SEAMLESS_GZ(  OPTBIT_GZIP        ,)
 	IF_FEATURE_SEAMLESS_Z(   OPTBIT_COMPRESS    ,) // 16th bit
+	IF_FEATURE_TAR_NOPRESERVE_TIME(OPTBIT_NOPRESERVE_TIME,)
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS
 	OPTBIT_NUMERIC_OWNER,
 	OPTBIT_NOPRESERVE_PERM,
@@ -769,6 +770,7 @@ enum {
 	OPT_INCLUDE_FROM = IF_FEATURE_TAR_FROM(     (1 << OPTBIT_INCLUDE_FROM)) + 0, // T
 	OPT_EXCLUDE_FROM = IF_FEATURE_TAR_FROM(     (1 << OPTBIT_EXCLUDE_FROM)) + 0, // X
 	OPT_GZIP         = IF_FEATURE_SEAMLESS_GZ(  (1 << OPTBIT_GZIP        )) + 0, // z
+	OPT_NOPRESERVE_TIME = IF_FEATURE_TAR_NOPRESERVE_TIME((1 << OPTBIT_NOPRESERVE_TIME)) + 0, // m
 	OPT_COMPRESS     = IF_FEATURE_SEAMLESS_Z(   (1 << OPTBIT_COMPRESS    )) + 0, // Z
 	OPT_NUMERIC_OWNER   = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NUMERIC_OWNER  )) + 0, // numeric-owner
 	OPT_NOPRESERVE_PERM = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NOPRESERVE_PERM)) + 0, // no-same-permissions
@@ -807,6 +809,9 @@ static const char tar_longopts[] ALIGN1 =
 # endif
 # if ENABLE_FEATURE_SEAMLESS_Z
 	"compress\0"            No_argument       "Z"
+# endif
+# if ENABLE_FEATURE_TAR_NOPRESERVE_TIME
+	"touch\0"               No_argument       "m"
 # endif
 	/* use numeric uid/gid from tar header, not textual */
 	"numeric-owner\0"       No_argument       "\xfc"
@@ -894,6 +899,7 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 		IF_FEATURE_TAR_FROM(     "T:X:")
 		IF_FEATURE_SEAMLESS_GZ(  "z"   )
 		IF_FEATURE_SEAMLESS_Z(   "Z"   )
+		IF_FEATURE_TAR_NOPRESERVE_TIME("m")
 		, &base_dir // -C dir
 		, &tar_filename // -f filename
 		IF_FEATURE_TAR_FROM(, &(tar_handle->accept)) // T
@@ -945,6 +951,11 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 	if (opt & OPT_COMPRESS)
 		get_header_ptr = get_header_tar_Z;
 
+#if ENABLE_FEATURE_TAR_NOPRESERVE_TIME
+	if (opt & OPT_NOPRESERVE_TIME)
+		tar_handle->ah_flags &= ~ARCHIVE_RESTORE_DATE;
+#endif
+
 #if ENABLE_FEATURE_TAR_FROM
 	tar_handle->reject = append_file_list_to_list(tar_handle->reject);
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS

include/usage.h

@@ -4408,7 +4408,7 @@
 #define tar_trivial_usage \
        "-[" IF_FEATURE_TAR_CREATE("c") IF_FEATURE_SEAMLESS_GZ("z") \
 	IF_FEATURE_SEAMLESS_BZ2("j") IF_FEATURE_SEAMLESS_LZMA("a") \
-	IF_FEATURE_SEAMLESS_Z("Z") "xtvO] " \
+	IF_FEATURE_SEAMLESS_Z("Z") IF_FEATURE_TAR_NOPRESERVE_TIME("m") "xtvO] " \
 	IF_FEATURE_TAR_FROM("[-X FILE] ") \
        "[-f TARFILE] [-C DIR] [FILE]..."
 #define tar_full_usage "\n\n" \
@@ -4433,6 +4433,9 @@
 	IF_FEATURE_SEAMLESS_Z( \
      "\n	Z	Filter the archive through compress" \
 	) \
+	IF_FEATURE_TAR_NOPRESERVE_TIME( \
+     "\n	m	Do not extract files modified time" \
+	) \
      "\nFile selection:" \
      "\n	f	Name of TARFILE or \"-\" for stdin" \
      "\n	O	Extract to stdout" \