Here is a handy tip to be able to install and update OSGeo4W packages, things like QGIS, GRASS, etc, using the apt utility from OSGeo4W. apt is a command line utility that you can install using OSGeo4W and then run using the OSGeo4W Shell.
First install apt via OSGeo4W
Now open the OSGeo4W Shell
from here you can run the apt utility.
The basic commands are apt update, apt install {package}, apt upgrade
Installing nightly QGIS
For a quick example we will install qgis-dev.
From the shell we can just run:
apt setup
apt update
apt install qgis-dev
apt will install all the needed dependencies
Done!
Script for updating nightly QGIS
So the good thing about using apt is if you wanted to make a quick batch file that you can run to update to the nightly build it's as simple as
@echo off
set OSGEO4W_ROOT=C:\OSGeo4W
set PATH=%OSGEO4W_ROOT%\bin;%PATH%
apt update
apt install qgis-dev
pause
Now you can just run the batch file to update your QGIS to the nightly build.
Extra tip
If you just want to upgrade all the packages you have installed you can do:
apt setup
apt upgrade
Simple