feat: Support using external git for initialization

[xxthunder]

• install.ps1 uses git for retrieval of Scoop and Main repo instead of downloading the zips.
• CI workflow runs install.ps1 and tests scoop availability after installation.

[xxthunder]

Our company's proxy forbids downloading the zipped repos (see ScoopInstaller/Scoop#5012 for details). So my workaround is to use 'git clone' instead when git is already installed (which is the case on our engineering machines). No idea if this is worth merging. Maybe it helps someone out there. 😄

[chawyehsu]

I don't mind leveraging the existing git command for bucket initialization. Still, similar to the downloader, you will need to pass potential proxy configs -NoProxy, -Proxy, -ProxyCredential, and -ProxyUseDefaultCredentials to git, so it can follow the proxy strategy when doing clones.

[xxthunder]

@chawyehsu Thank you very much for your feedback. Currently we are using environment variables for doing this: HTTP_PROXY, HTTPS_PROXY and NO_PROXY. So no need for command line arguments.

[chawyehsu]

That's perfectly fine when you are using proxy environment variables, what I mean is if you do not pass those proxy settings to the git command, then other users who use irm get.scoop.sh -Proxy 'http://<ip:port>' | iex to install Scoop without configuring proxy environment variables will not be able to clone/initialize buckets because git is not configured to use the prxoy -Proxy 'http://<ip:port>'.

Install/install.ps1

Lines 43 to 50 in f1cf244

	.PARAMETER NoProxy
	Bypass system proxy during the installation.
	.PARAMETER Proxy
	Specifies proxy to use during the installation.
	.PARAMETER ProxyCredential
	Specifies credential for the given prxoy.
	.PARAMETER ProxyUseDefaultCredentials
	Use the credentials of the current user for the proxy server that is specified by the -Proxy parameter.

Install/install.ps1

Lines 175 to 199 in f1cf244

	function Get-Downloader {
	$downloadSession = New-Object System.Net.WebClient
	# Set proxy to null if NoProxy is specificed
	if ($NoProxy) {
	$downloadSession.Proxy = $null
	} elseif ($Proxy) {
	# Prepend protocol if not provided
	if (!$Proxy.IsAbsoluteUri) {
	$Proxy = New-Object System.Uri("http://" + $Proxy.OriginalString)
	}
	$Proxy = New-Object System.Net.WebProxy($Proxy)
	if ($null -ne $ProxyCredential) {
	$Proxy.Credentials = $ProxyCredential.GetNetworkCredential()
	} elseif ($ProxyUseDefaultCredentials) {
	$Proxy.UseDefaultCredentials = $true
	}
	$downloadSession.Proxy = $Proxy
	}
	return $downloadSession
	}

[xxthunder]

Aaah, yes, now I got your point. Looking into it, will come back to you.

[xxthunder]

Okay, got the scoop installer and finally scoop running in GitHub action to see that it is actually working. @chawyehsu Any feedback is welcome.

By the way, green finally: https://github.com/xxthunder/ScoopInstall/actions/runs/4114136831

[xxthunder]

@chawyehsu Finally found some time again. Thanks for pointing me to this Invoke-Git function. So I took over the env vars recovery. Tests are green: https://github.com/xxthunder/ScoopInstall/actions/runs/4368498689

Please review again when you have time.

[chawyehsu]

Thank you for your contributions! 🎉

[chawyehsu]

Just noticed this will actually trigger an installation of Scoop, it tries to expose functions for unit tests below but it imports the whole install script. I noticed it when implementing #76 and the ci kept failing. ;p