[packit] 0.28.0 upstream release

Upstream tag: 0.28.0
Upstream commit: cdf06f20

plans/git_reference.py

@@ -1,5 +1,8 @@
 #!/usr/bin/python
 
+# Copyright Contributors to the Packit project.
+# SPDX-License-Identifier: MIT
+
 import subprocess
 from pathlib import Path
 

plans/main.fmf

@@ -1,6 +1,6 @@
 discover:
     how: fmf
     url: https://github.com/packit/specfile.git
-    ref: 1789f9c67c37da87ffdc967ad9311c4881013077
+    ref: cdf06f20715f661b1a5f478320eee2b48c2ba287
 execute:
     how: tmt

plans/packit-integration.fmf

@@ -2,7 +2,7 @@ discover:
     how: fmf
     url: https://github.com/packit/packit
     filter: tier:0 | tier:1
-    ref: f3df29535cfdefd44febe79cb4a883627c085db0
+    ref: 0048024ec6564008a703140254c4394158b6ed67
 prepare:
   - how: install
     copr: packit/packit-dev