README: document multi-partition setup and auto slot detection

README.md

@@ -33,7 +33,7 @@ __do.cleanup=0__ will keep the zip from removing it's working directory in /tmp/
 
 __do.cleanuponabort=0__ will keep the zip from removing it's working directory in /tmp/anykernel in case of installation abort.
 
-`is_slot_device=1` enables detection of the suffix for the active boot partition on slot-based devices and will add this to the end of the supplied `block=` path.
+`is_slot_device=1` enables detection of the suffix for the active boot partition on slot-based devices and will add this to the end of the supplied `block=` path. Also accepts `auto` for use with broad, device non-specific zips.
 
 `ramdisk_compression=auto` allows automatically repacking the ramdisk with the format detected during unpack, changing `auto` to `gz`, `lzo`, `lzma`, `xz`, `bz2`, `lz4`, or `lz4-l` (for lz4 legacy) instead forces the repack as that format.
 
@@ -73,6 +73,8 @@ __"block|mount|fstype|options|flags"__ requires you specify which part (listed i
 
 _dump_boot_ and _write_boot_ are the default method of unpacking/repacking, but for more granular control, or omitting ramdisk changes entirely ("OG AK" mode), these can be separated into _split_boot; unpack_ramdisk_ and _repack_ramdisk; flash_boot_ respectively.
 
+Multi-partition zips can be created by removing the ramdisk and patch folders from the zip and including instead "-files" folders named for the partition (without slot suffix), e.g. boot-files + recovery-files, or kernel-files + ramdisk-files (on some Treble devices). These then contain zImage, and ramdisk, patch, etc. subfolders for each partition. To setup for the next partition, simply set `block=` and `ramdisk_compression=` for the new target partition and use the _reset_ak_ command.
+
 _backup_file_ may be used for testing to ensure ramdisk changes are made correctly, transparency for the end-user, or in a ramdisk-only "mod" zip. In the latter case _restore_file_ could also be used to create a "restore" zip to undo the changes, but should be used with caution since the underlying patched files could be changed with ROM/kernel updates.
 
 You may also use _ui_print "\<text\>"_ to write messages back to the recovery during the modification process, and _file_getprop "\<file\>" "\<property\>"_ and _contains "\<string\>" "\<substring\>"_ to simplify string testing logic you might want in your script.