Documentation on Android CLI options

[zach-morris]

Describe the bug
No documentation on the android CLI / activity manager options

Expected behavior/changes
Included documentation on the android CLI / activity manager options

Additional context
Reference: https://forums.libretro.com/t/retroarch-cli-for-android/32002/2

Just requesting some documentation on starting / launching RA from the CLI on android.

When starting RA from an activity manager or the CLI on android, what do all the different options actually do, and which are required?

Most of the info I could glean on them is directly from the git source code and this super helpful page for the pegasus front end launcher.

There’s a myriad of flags, but I can’t fully understand what they all do:

am start --user 0
  -n com.retroarch/.browser.retroactivity.RetroActivityFuture
  -e ROM {file path}. #Required
  -e LIBRETRO {core path} #Required
  -e CONFIGFILE {config file path} #Required
  -e IME com.android.inputmethod.latin/.LatinIME #Standard android fluff as far as i can tell, and its required otherwise the app wont launch
  -e DATADIR /data/data/com.retroarch ???  What is this needed for, if at all?
  -e APK /data/app/com.retroarch-1/base.apk ???  What is this needed for, if at all?
  -e SDCARD /storage/emulated/0 ???  What is this needed for, if at all?
  -e EXTERNAL /storage/emulated/0/Android/data/com.retroarch/files ???  What is this needed for, if at all?
  --activity-clear-task   #Will basically 'start fresh' the application, if I'm reading the docs correctly:  https://developer.android.com/reference/android/content/Intent#FLAG_ACTIVITY_CLEAR_TASK
  --activity-clear-top. #Use the running instance of the app if its already open, if I'm reading the docs correctly:  https://developer.android.com/reference/android/content/Intent#FLAG_ACTIVITY_CLEAR_TOP
  --activity-no-history. #Prevent any android gui stuff getting in the way of launching, if I'm reading the docs correctly:  https://developer.android.com/reference/android/content/Intent#FLAG_ACTIVITY_NO_HISTORY