Add admin.repos.* qrexec services

This is a prerequisite for QubesOS/qubes-issues#4550.

qubes-rpc-policy/admin.repos.Disable

@@ -0,0 +1,7 @@
+## Note that policy parsing stops at the first match,
+## so adding anything below "$anyvm $anyvm action" line will have no effect
+
+## Please use a single # to start your custom comments
+
+dom0	dom0	allow
+$anyvm	$anyvm	deny

qubes-rpc-policy/admin.repos.Enable

@@ -0,0 +1,7 @@
+## Note that policy parsing stops at the first match,
+## so adding anything below "$anyvm $anyvm action" line will have no effect
+
+## Please use a single # to start your custom comments
+
+dom0	dom0	allow
+$anyvm	$anyvm	deny

qubes-rpc-policy/admin.repos.List

@@ -0,0 +1,7 @@
+## Note that policy parsing stops at the first match,
+## so adding anything below "$anyvm $anyvm action" line will have no effect
+
+## Please use a single # to start your custom comments
+
+dom0	dom0	allow
+$anyvm	$anyvm	deny

qubes-rpc/admin.repos.Disable

@@ -0,0 +1,24 @@
+#!/usr/bin/python3
+
+# Empty output indicates success; any input indicates error (probably an exception)
+
+import dnf
+import iniparse
+import sys
+
+base = dnf.Base()
+
+base.read_all_repos()
+
+reponame = sys.stdin.readline()
+repo = base.repos[reponame]
+
+# Loosely based on write_raw_configfile() from DNF source code,
+# because that method was introduced in DNF 2.0 but Qubes dom0 has DNF 1.x.
+with open(repo.repofile) as fp:
+	ini = iniparse.INIConfig(fp)
+
+ini[reponame]['enabled'] = 0
+
+with open(repo.repofile, 'w') as fp:
+	fp.write(str(ini))

qubes-rpc/admin.repos.Enable

@@ -0,0 +1,24 @@
+#!/usr/bin/python3
+
+# Empty output indicates success; any input indicates error (probably an exception)
+
+import dnf
+import iniparse
+import sys
+
+base = dnf.Base()
+
+base.read_all_repos()
+
+reponame = sys.stdin.readline()
+repo = base.repos[reponame]
+
+# Loosely based on write_raw_configfile() from DNF source code,
+# because that method was introduced in DNF 2.0 but Qubes dom0 has DNF 1.x.
+with open(repo.repofile) as fp:
+	ini = iniparse.INIConfig(fp)
+
+ini[reponame]['enabled'] = 1
+
+with open(repo.repofile, 'w') as fp:
+	fp.write(str(ini))

qubes-rpc/admin.repos.List

@@ -0,0 +1,11 @@
+#!/usr/bin/python3
+
+import dnf
+
+base = dnf.Base()
+
+base.read_all_repos()
+
+for repo in base.repos.all():
+	l = [repo.id, repo.name, 'enabled' if repo.enabled else 'disabled']
+	print('\0'.join(l))