[sailfishos-chum-repo-config.spec] Require SailfishOS ≥ 3.1.0

rpm/sailfishos-chum-repo-config.spec

@@ -17,6 +17,10 @@ Source99:       %{name}.rpmlintrc
 Requires:       ssu
 Requires(post): ssu
 Requires(postun): ssu
+# The oldest SailfishOS release which SailfishOS:Chum supports, because it is the
+# oldest useable DoD-repo at https://build.sailfishos.org/project/subprojects/sailfishos
+Requires:       sailfish-version >= 3.1.0
+# Provide (anti-)dependencies to sibling packages:
 Conflicts:      sailfishos-chum-repo-config-testing
 Obsoletes:      sailfishos-chum-repo-config-testing
 Conflicts:      sailfishos-chum-testing
@@ -129,7 +133,7 @@ Url:
 %post
 # The %%post scriptlet is deliberately run when installing and updating.
 # Add sailfishos-chum repository configuration, depending on the installed
-# SailfishOS release (3.1.0 is the lowest supported, see line 62):
+# SailfishOS release (3.1.0 is the lowest supported, see line 22):
 source %{_sysconfdir}/os-release
 # Three equivalent variants, but the sed-based ones have additional, ugly
 # backslashed quoting of all backslashes, curly braces and brackets (likely