Support MIUI OS backup file

[LeonDevLifeLog]

No description provided.

[nelenkov]

Could you share some docs/info about MIUI OS backup format?

[LeonDevLifeLog]

MIUI os backup app just add custom magic header info before android origin backup file header.
MIUI os custom magic header are split by \n,so just skip five line from the file header.

[rustyx]

Don't you want to be able to write such format, too?

[Zipper-1]

The majority of MIUI BACKUP magic Header is unchanged across packages with the following format. Repacking is quite easy by simply adding the header to repacked Android backup package. Note: there is a blank space between package name and app name.

MIUI BACKUP
2
<packageName> <appDisplayName(UTF-8)>
-1
0

[nelenkov]

There is an outstanding PR for this, if someone can test that it actually works with MIUI backup (and doesn't break regular Android backup), I can merge it.