Mention PowerShell Repository

Added a section about the PowerShell Gallery and how to pull and update PowerShell Modules from there.

Author: Klaus Frank

book/A-git-in-other-environments/sections/powershell.asc

@@ -10,12 +10,33 @@ It looks like this:
 .Powershell with Posh-git.
 image::images/posh-git.png[Powershell with Posh-git.]
 
-Just download a Posh-Git release from (https://github.com/dahlbyk/posh-git[]), and uncompress it to the `WindowsPowershell` directory.
-Then open a Powershell prompt as the administrator, and do this:
+==== Installation
+===== Prerequisites
+Before you're able to run PowerShell scripts on your machine, you need to set your local ExecutionPolicy to RemoteSigned (Basically anything except Undefined and Restricted). If you choose AllSigned instead of RemoteSigned, also local scripts (your own) need to be digitally signed in order to be executed. With RemoteSigned, only Scripts having the "ZoneIdentifier" set to Internet (were downloaded from the web) need to be signed, others not.
+If you're an administrator and want to set it for all Users on that machine, use "-Scope LocalMachine".
+If you're a normal user, without administrative rights, you can use "-Scope CurrentUser" to set it only for you.
+More about PowerShell Scopes: (https://technet.microsoft.com/de-de/library/hh847849.aspx[])
+More about PowerShell ExecutionPolicy: (https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.security/set-executionpolicy[])
+[source,powershell]
+-----
+> Set-ExecutionPolicy -Scope LocalMachine -ExecutionPolicy RemoteSigned -Force
+-----
 
+===== PowerShell Gallery
+If you have at least PowerShell 5 or PowerShell 4 with PackageManagement installed, you can use the package manager to fetch Posh-Git for you.
+More information about the requirements: (https://docs.microsoft.com/en-us/powershell/gallery/psget/get_psget_module[])
+[source,powershell]
+-----
+> Update-Module PowerShellGet -Force
+> Install-Module Posh-Git -Scope LocalMachine
+-----
+If you want to install Posh-Git only for the currnet user and not globaly, use "-Scope CurrentUser" instead.
+
+===== From Source
+Just download a Posh-Git release from (https://github.com/dahlbyk/posh-git[]), and uncompress it to the `WindowsPowershell` directory.
+Then open a Powershell prompt as an administrator, and do this:
 [source,powershell]
 -----
-> Set-ExecutionPolicy RemoteSigned -Scope CurrentUser -Confirm
 > cd ~\Documents\WindowsPowerShell\posh-git
 > .\install.ps1
 -----