Add Chris Demetriou's --unlink changes.

I know that I said earlier that this should be unconditional behaviour,
but I thought about it a little more and concluded that the principle of least
surprise dictates that I make it an option.

gnu/usr.bin/tar/extract.c

@@ -310,6 +310,14 @@ extract_archive ()
 	  fd = 1;
 	  goto extract_file;
 	}
+
+      if (f_unlink && !f_keep) {
+	if (unlink(skipcrud + current_file_name) == -1)
+		if (errno != ENOENT)
+		   msg_perror ("Could not unlink %s",
+                      skipcrud + current_file_name);
+      }
+
 #ifdef O_CTG
       /*
 		  * Contiguous files (on the Masscomp) have to specify
@@ -556,6 +564,13 @@ extract_archive ()
       {
 	struct stat st1, st2;
 
+        if (f_unlink && !f_keep) {
+	  if (unlink(skipcrud + current_file_name) == -1)
+		if (errno != ENOENT)
+		   msg_perror ("Could not unlink %s",
+                      skipcrud + current_file_name);
+        }
+
 	check = link (current_link_name, skipcrud + current_file_name);
 
 	if (check == 0)
@@ -578,6 +593,13 @@ extract_archive ()
 #ifdef S_ISLNK
     case LF_SYMLINK:
     again_symlink:
+      if (f_unlink && !f_keep) {
+	  if (unlink(skipcrud + current_file_name) == -1)
+		if (errno != ENOENT)
+		   msg_perror ("Could not unlink %s",
+                      skipcrud + current_file_name);
+      }
+
       check = symlink (current_link_name,
 		       skipcrud + current_file_name);
       /* FIXME, don't worry uid, gid, etc... */
@@ -602,6 +624,13 @@ extract_archive ()
 #endif
 #if defined(S_IFCHR) || defined(S_IFBLK)
     make_node:
+      if (f_unlink && !f_keep) {
+	  if (unlink(skipcrud + current_file_name) == -1)
+		if (errno != ENOENT)
+		   msg_perror ("Could not unlink %s",
+                      skipcrud + current_file_name);
+      }
+
       check = mknod (current_file_name + skipcrud,
 		     (int) hstat.st_mode, (int) hstat.st_rdev);
       if (check != 0)
@@ -619,6 +648,13 @@ extract_archive ()
       /* If local system doesn't support FIFOs, use default case */
     case LF_FIFO:
     make_fifo:
+      if (f_unlink && !f_keep) {
+	  if (unlink(skipcrud + current_file_name) == -1)
+		if (errno != ENOENT)
+		   msg_perror ("Could not unlink %s",
+                      skipcrud + current_file_name);
+      }
+
       check = mkfifo (current_file_name + skipcrud,
 		      (int) hstat.st_mode);
       if (check != 0)

gnu/usr.bin/tar/tar.c

@@ -181,6 +181,8 @@ struct option long_options[] =
   {"force-local", 0, &f_force_local, 1},
   {"atime-preserve", 0, &f_atime_preserve, 1},
 
+  {"unlink", 0, &f_unlink, 1},
+
   {0, 0, 0, 0}
 };
 
@@ -757,6 +759,7 @@ Other options:\n\
 			filter the archive through PROG (which must accept -d)\n\
 --block-compress	block the output of compression program for tapes\n\
 -[0-7][lmh]		specify drive and density\n\
+--unlink		unlink files before creating them\n\
 ", stdout);
 }
 

gnu/usr.bin/tar/tar.h

@@ -231,6 +231,7 @@ TAR_EXTERN char *f_volno_file;	/* --volno-file */
 TAR_EXTERN int f_force_local;	/* --force-local */
 TAR_EXTERN int f_atime_preserve;/* --atime-preserve */
 TAR_EXTERN int f_compress_block; /* --compress-block */
+TAR_EXTERN int f_unlink;	/* --unlink */
 
 /*
  * We default to Unix Standard format rather than 4.2BSD tar format.