Add a FAQ in readme. Fixes #4

Author: samuelchemla

readme.md

@@ -1,4 +1,4 @@
-# easysync
+# EasySync
 
 Synchronize your phone with your DAV server, the easy way. 
 
@@ -11,6 +11,44 @@ Synchronize your phone with your DAV server, the easy way.
 * Secure storage of your credentials
 * Preserve timestamps if you use Nextcloud as DAV server
 
+## FAQ
+
+### What is synchronized
+* **Images, video, screenshots**
+  * If they are displayed in your gallery, they will be synchronized. This includes images and videos in `DCIM/`, `Pictures/`, `Movies/` and `Download/`
+  * If they are only available in a specific app but not in gallery, they won't be synchronized
+  * Please note that messaging apps (messages, whatsapp, signal, etc.) generally offer you the choice between saving files in your gallery (in such case they will be synchronized) or not
+* **Audio, music**
+  * All audio files that are visible in `Alarms/`, `Audiobooks/`, `Music/`, `Notifications/`, `Podcasts/`, `Ringtones/` and `Recordings/` will be synchronized
+  * Beware that google's own voice recorder stores its files privately and offer its own cloud synchronization. They won't be synchronized by EasySync
+* **Downloaded files**
+  * All downloaded files in `Download/` will be synchronized, whether they are pdf, epubs, documents, images, etc.
+
+### What is not synchronized
+Everything not explicitly stated above is not synchronized. More specifically:
+* Applications
+* Applications data/state
+* Messages
+* Contacts
+* Games progress
+* Wifi or network parameters
+* Android settings and phone customization
+
+### Can I choose what is synchronized
+No
+
+### I am a nextcloud user. Does this replace nextcloud app?
+When you configure EasySync you select a specific folder on your DAV server. This folder will be fully synced with your phone.
+
+If you want to access files on your DAV server that are outside that specific folder, then you still need nextcloud app. Otherwise it is probably not necessary.
+
+### Changes on android device side are not immediately reflected
+1. Please be sure to disable battery optimization permission (it will be shown on home screen if required). Disabling battery optimization will not drain your battery. It will just enable immediate sync of file changes.
+2. You may also enable `Sync on cellular` and/or `Sync on battery` in `Synchronization settings` (available from home screen).
+
+### Changes on DAV side are not immediately reflected
+In order to preserve battery we cannot detect quickly DAV changes. If you need immediate sync use "Sync now" button on home screen.
+
 ## Supported Android phones
 * From Android 8 to latest releases
 * Huawei phones may kill the app in background, be warned. These tips will help you:
@@ -25,7 +63,7 @@ It should work with any DAV compliant server.
 ## Sync is slow on Nextcloud
 There are several reports of nextcloud DAV to be slow.
 
-You can get drastic speedup (almost 10x) when using a device password instead of your user's password:
+You can get **drastic speedup** (almost 10x) when using a device password instead of your user's password:
 1. Create a [device password](https://docs.nextcloud.com/server/19/user_manual/session_management.html#managing-devices)
 2. Go to DAV Settings in easysync, use your own login, but put the device password instead of your usual user password
 3. Enjoy 10x speedup