Update README.md, add notice about perms/ownership

README.md

@@ -45,13 +45,16 @@ API calls.
       Note that by default Username is preferred over UID
     --extract-prefer-gid : Prefer GID over Group when extracting
       Note that by default Group is preferred over UID
+    --map-user <UID/Uname>:<UID/Uname> : Maps a UID/Username to UID/Username
+    --map-group <GID/Gname>:<GID/Gname> : Maps a GID/Group to GID/Group
     --force-file-permissions <3-octal-values> : Force set permissions for files on archive creation/extraction
       Must be three octal characters like "755" or "440"
     --force-dir-permissions <3-octal-values> : Force set permissions for directories on archive creation/extraction
       Must be three octal characters like "755" or "440"
     -- : specifies remaining arguments are files to archive/extract
     If creating archive file, remaining args specify files to archive.
     If extracting archive file, remaining args specify files to extract.
+    Note that permissions/ownership/remapping is saved when archiving, but when extracting they are only preserved when extracting as root!
 
 Note that `--compressor` and `--decompressor` cmds must accept data from stdin
 and return processed data to stdout.

src/parser.c

@@ -243,6 +243,10 @@ void simple_archiver_print_usage(void) {
   fprintf(
       stderr,
       "If extracting archive file, remaining args specify files to extract.\n");
+  fprintf(stderr,
+          "Note that permissions/ownership/remapping is saved when archiving, "
+          "but when extracting they are only preserved when extracting as root!"
+          "\n");
 }
 
 SDArchiverParsed simple_archiver_create_parsed(void) {