Add apt pin to branch repos

This adds apt pin to branch repos, this is higher priority then what we
ship default. This makes sure it installs the requested branch
regardless if version.

Author: mariogrip

ubports-qa

@@ -102,13 +102,18 @@ def list_exists(branch):
     return os.path.isfile(get_list_file(branch))
 
 
+def pref_exists(branch):
+    return os.path.isfile(get_pref_file(branch))
+
+
 def list_lists():
     return [
         f.split("ubports-")[1].split(".list")[0]
         for f in os.listdir("/etc/apt/sources.list.d/")
         if os.path.isfile("/etc/apt/sources.list.d/" + f) and f.startswith("ubports-")
     ]
 
+
 def add_list(branch):
     if list_exists(branch):
         return
@@ -118,13 +123,31 @@ def add_list(branch):
         repo_list.write("deb http://repo.ubports.com/ {} main".format(branch))
 
 
+def add_pref(branch):
+    if pref_exists(branch):
+        return
+    with open(get_pref_file(branch), "w+") as pref:
+        # TODO: edit and set own pin priority to allow up/down/side-grade without
+        # removal of repo etc
+        pref.write("Package: *\n"
+                   "Pin: release o=UBports,a={}\n"
+                   "Pin-Priority: 2000\n".format(branch))
+
+
 def remove_list(branch):
     # If it does not exist, just ignore
     if not list_exists(branch):
         return
     os.remove(get_list_file(branch))
 
 
+def remove_pref(branch):
+    # If it does not exist, just ignore
+    if not pref_exists(branch):
+        return
+    os.remove(get_pref_file(branch))
+
+
 def get_github_pr(repo, num):
     pull_request_url = GITHUB_API_PULLREQUEST.format(repo=repo, num=num)
     LOG.debug("Getting pull request information from " + pull_request_url)
@@ -180,6 +203,7 @@ def install_command(args):
 
     with WritableRootFS():
         add_list(repository_name)
+        add_pref(repository_name)
         apt_update()
         apt_upgrade()
 
@@ -198,6 +222,7 @@ def remove_command(args):
         die("Repo {} is not installed".format(repository))
     with WritableRootFS():
         remove_list(repository)
+        remove_pref(repository)
         apt_update()
         apt_upgrade()