https://github.com/msys2/msys2-installer/releases/tag/nightly-x86_64
Installing the GUI installer via the CLI to C:\msys64:
.\msys2-x86_64-latest.exe in --confirm-command --accept-messages --root C:/msys64
Uninstalling an existing installation in C:\msys64 via the CLI:
C:\msys64\uninstall.exe pr --confirm-command
Installing the self extracting archive to C:\msys64:
.\msys2-base-x86_64-latest.sfx.exe -y -oC:\
The installer provides some additional features such as installing shortcuts, registering an uninstaller, a GUI for selecting the installation path and automatically running a login shell at the end to initialize the MSYS2 environment.
If you unpack the archives and run a login shell once, you will get a functionally equivalent MSYS2 installation.
It contains the base package and all its dependencies. You can list the contained packages using: pactree base -lu | sort