README: update for multi-slot zip instructions

README.md

@@ -42,8 +42,9 @@ __supported.versions=__ will match against ro.build.version.release from the cur
 
 `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, and using `cpio` or `none` will force the repack as uncompressed.
 
-`customdd="<arguments>"` may be added to allow specifying additional dd parameters for 
-devices that need to hack their kernel directly into a large partition like mmcblk0.
+`customdd="<arguments>"` may be added to allow specifying additional dd parameters for devices that need to hack their kernel directly into a large partition like mmcblk0.
+
+`slot_select=<active|inactive>` may be added to allow specifying the target slot. If omitted the default remains `active`.
 
 ## // Command Methods ##
 ```
@@ -69,7 +70,7 @@ patch_ueventd <ueventd file> <device node> <permissions> <chown> <chgrp>
 repack_ramdisk
 flash_boot
 write_boot
-reset_ak
+reset_ak [keep]
 flash_dtbo
 ```
 
@@ -85,7 +86,9 @@ __"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. _flash_dtbo_ can be used to flash a dtbo image. It is automatically included in _write_boot_ but can be called separately if using "OG AK" mode or creating a dtbo only zip.
 
-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.
+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=` (without slot suffix) and `ramdisk_compression=` for the new target partition and use the _reset_ak_ command.
+
+Similarly, multi-slot zips can be created with the normal zip layout for the active (current) slot, then resetting for the inactive slot by setting `block=` (without slot suffix) again, `slot_select=inactive` and `ramdisk_compression=` for the target slot and using the _reset_ak keep_ command, which will retain the patch and AK2 added ramdisk files for the next slot.
 
 _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.