test for parsing option as list

cabal-testsuite/PackageTests/UserConfig/cabal.out

@@ -6,3 +6,9 @@ cabal: <ROOT>/cabal.dist/cabal-config already exists.
 Writing default configuration to <ROOT>/cabal.dist/cabal-config
 # cabal user-config
 Writing default configuration to <ROOT>/cabal.dist/cabal-config2
+# cabal user-config
+Renaming <ROOT>/cabal.dist/cabal-config to <ROOT>/cabal.dist/cabal-config.backup.
+Writing merged config to <ROOT>/cabal.dist/cabal-config.
+# cabal user-config
+Renaming <ROOT>/cabal.dist/cabal-config to <ROOT>/cabal.dist/cabal-config.backup.
+Writing merged config to <ROOT>/cabal.dist/cabal-config.

cabal-testsuite/PackageTests/UserConfig/cabal.test.hs

@@ -11,3 +11,7 @@ main = cabalTest $ do
     withEnv [("CABAL_CONFIG", Just conf2)] $ do
         cabal "user-config" ["init"]
         shouldExist conf2
+    cabalG ["--config-file", conf] "user-config" ["update", "-f", "-a", "extra-prog-path: foo", "-a", "extra-prog-path: bar"]
+    assertFileDoesContain conf "foo,bar"
+    cabalG ["--config-file", conf] "user-config" ["update", "-f", "-a", "extra-prog-path: foo, bar"]
+    assertFileDoesContain conf "foo,bar"