feat: allow selecting alternate salt package repositories

Make the upstream salt package repository selectable, thus allowing the
use of archived salt versions (hosted in
https://archive.repo.saltproject.io), as well as custom salt versions
hosted in alternate repositories.

pillar.example

     salt_ssh: 'salt-ssh'
     pyinotify: 'python-pyinotify'  # the package to be installed for pyinotify
 
+  # Set which salt repository to use, default to https://repo.saltstack.com
+  # For older releases use https://archive.repo.saltproject.io
+  repo: 'https://archive.repo.saltproject.io'
+
   # Set which release of SaltStack to use, default to 'latest'
   # To get the available releases:
   # * http://repo.saltstack.com/yum/redhat/7/x86_64/

salt/osfamilymap.yaml

 {%- set osmajorrelease = salt['grains.get']('osmajorrelease', osrelease)|string %}
 {%- set oscodename = salt['grains.get']('oscodename') %}
 {%- set opensuse_repo_suffix = 'Leap_' ~ osrelease if salt['grains.get']('osfinger', '') == 'Leap-15' else 'Tumbleweed' %}
+{%- set salt_repo = salt['pillar.get']('salt:repo', 'https://repo.saltstack.com') %}
 
 #from template-formula
 {%- if grains.os_family == 'MacOS' %}
 
 
 Debian:
-  pkgrepo: 'deb http://repo.saltstack.com/{{ py_ver_repr or 'apt' }}/{{ osfamily_lower }}/{{ osmajorrelease }}/amd64/{{ salt_release }} {{ oscodename }} main'
-  key_url: 'https://repo.saltstack.com/{{ py_ver_repr or 'apt' }}/{{ osfamily_lower }}/{{ osmajorrelease }}/amd64/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
+  pkgrepo: 'deb {{ salt_repo }}/{{ py_ver_repr or 'apt' }}/{{ osfamily_lower }}/{{ osmajorrelease }}/amd64/{{ salt_release }} {{ oscodename }} main'
+  key_url: '{{ salt_repo }}/{{ py_ver_repr or 'apt' }}/{{ osfamily_lower }}/{{ osmajorrelease }}/amd64/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
   libgit2: libgit2-22
   pyinotify: python-pyinotify
   gitfs:
 RedHat:
   pkgrepo_name: saltstack
   pkgrepo_humanname: SaltStack repo for RHEL/CentOS $releasever
-  pkgrepo: 'https://repo.saltstack.com/{{ py_ver_repr or 'yum' }}/redhat/$releasever/$basearch/{{ salt_release }}'
-  key_url: 'https://repo.saltstack.com/{{ py_ver_repr or 'yum' }}/redhat/$releasever/$basearch/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
+  pkgrepo: '{{ salt_repo }}/{{ py_ver_repr or 'yum' }}/redhat/$releasever/$basearch/{{ salt_release }}'
+  key_url: '{{ salt_repo }}/{{ py_ver_repr or 'yum' }}/redhat/$releasever/$basearch/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
   pygit2: python-pygit2
   python_git: GitPython
   gitfs:

salt/osmap.yaml

 {% set osmajorrelease = salt['grains.get']('osmajorrelease', osrelease)|string %}
 {% set oscodename = salt['grains.get']('oscodename') %}
 {% set os_family_lower =  salt['grains.get']('os_family')|lower %}
+{% set salt_repo = salt['pillar.get']('salt:repo', 'https://repo.saltstack.com') %}
 
 Fedora:
   pygit2: python2-pygit2
 Amazon:
   pkgrepo_name: saltstack-amzn-repo
   pkgrepo_humanname: SaltStack repo for Amazon Linux 2
-  pkgrepo: 'https://repo.saltstack.com/{{ py_ver_dir or 'yum' }}/amazon/2/$basearch/{{ salt_release }}'
-  key_url: 'https://repo.saltstack.com/{{ py_ver_dir or 'yum' }}/amazon/2/$basearch/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
+  pkgrepo: '{{ salt_repo }}/{{ py_ver_dir or 'yum' }}/amazon/2/$basearch/{{ salt_release }}'
+  key_url: '{{ salt_repo }}/{{ py_ver_dir or 'yum' }}/amazon/2/$basearch/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
 
 Ubuntu:
-  pkgrepo: 'deb http://repo.saltstack.com/{{ py_ver_dir or 'apt' }}/{{ os_lower }}/{{ osrelease }}/amd64/{{ salt_release }} {{ oscodename }} main'
-  key_url: 'https://repo.saltstack.com/{{ py_ver_dir or 'apt' }}/{{ os_lower }}/{{ osrelease }}/amd64/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
+  pkgrepo: 'deb {{ salt_repo }}/{{ py_ver_dir or 'apt' }}/{{ os_lower }}/{{ osrelease }}/amd64/{{ salt_release }} {{ oscodename }} main'
+  key_url: '{{ salt_repo }}/{{ py_ver_dir or 'apt' }}/{{ os_lower }}/{{ osrelease }}/amd64/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
   pygit2: python-pygit2
   gitfs:
     pygit2:
         install_from_package: Null
 
 Raspbian:
-  pkgrepo: 'deb http://repo.saltstack.com/{{ py_ver_dir or 'apt' }}/{{ os_family_lower }}/{{ osmajorrelease }}/armhf/{{ salt_release }} {{ oscodename }} main'
-  key_url: 'https://repo.saltstack.com/{{ py_ver_dir or 'apt' }}/{{ os_family_lower }}/{{ osmajorrelease }}/armhf/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
+  pkgrepo: 'deb {{ salt_repo }}/{{ py_ver_dir or 'apt' }}/{{ os_family_lower }}/{{ osmajorrelease }}/armhf/{{ salt_release }} {{ oscodename }} main'
+  key_url: '{{ salt_repo }}/{{ py_ver_dir or 'apt' }}/{{ os_family_lower }}/{{ osmajorrelease }}/armhf/{{ salt_release }}/SALTSTACK-GPG-KEY.pub'
 
 SmartOS:
   salt_master: salt