Enable building arbitrary forks and branches

docker/unstable/bootstrap.ps1

@@ -1,6 +1,6 @@
 # This is intended to be used inside Docker containers
 
-git clone --recursive https://github.com/PowerShell/PowerShell.git
+git clone --recursive https://github.com/$env:fork/PowerShell.git -b $env:branch
 Set-Location PowerShell
 Import-Module ./build.psm1
 Start-PSBootstrap -Package -NoSudo

docker/unstable/centos7/Dockerfile

@@ -1,6 +1,9 @@
 FROM powershell/powershell:stable-centos7
 MAINTAINER Andrew Schwartzmeyer <andschwa@microsoft.com>
 
+ARG fork=PowerShell
+ARG branch=master
+
 COPY bootstrap.ps1 /
 RUN powershell -f bootstrap.ps1 \
     && yum install -y PowerShell/powershell*.rpm

docker/unstable/ubuntu14.04/Dockerfile

@@ -1,6 +1,9 @@
 FROM powershell/powershell:stable-ubuntu14.04
 MAINTAINER Andrew Schwartzmeyer <andschwa@microsoft.com>
 
+ARG fork=PowerShell
+ARG branch=master
+
 COPY bootstrap.ps1 /
 RUN powershell -f bootstrap.ps1 \
     && dpkg -i PowerShell/powershell*.deb

docker/unstable/ubuntu16.04/Dockerfile

@@ -1,6 +1,9 @@
 FROM powershell/powershell:stable-ubuntu16.04
 MAINTAINER Andrew Schwartzmeyer <andschwa@microsoft.com>
 
+ARG fork=PowerShell
+ARG branch=master
+
 COPY bootstrap.ps1 /
 RUN powershell -f bootstrap.ps1 \
     && dpkg -i PowerShell/powershell*.deb