Test that 'cabal user-config init' uses CABAL_CONFIG.

cabal-install/cabal-install.cabal

@@ -66,6 +66,8 @@ Extra-Source-Files:
   tests/IntegrationTests/user-config/should_run/overwrites_with_f.sh
   tests/IntegrationTests/user-config/should_run/runs_without_error.out
   tests/IntegrationTests/user-config/should_run/runs_without_error.sh
+  tests/IntegrationTests/user-config/should_run/uses_CABAL_CONFIG.out
+  tests/IntegrationTests/user-config/should_run/uses_CABAL_CONFIG.sh
 
 source-repository head
   type:     git

cabal-install/tests/IntegrationTests.hs

@@ -264,7 +264,9 @@ main = do
   -- Set up environment variables for test scripts
   setEnv "GHC_PKG" $ programPath ghcPkg
   setEnv "CABAL" $ programPath cabal
+  -- Define default arguments
   setEnv "CABAL_ARGS" $ "--config-file=config-file"
+  setEnv "CABAL_ARGS_NO_CONFIG_FILE" " "
   -- Discover all the test caregories
   categories <- discoverTestCategories baseDirectory
   -- Discover tests in each category

cabal-install/tests/IntegrationTests/user-config/common.sh

 # Helper to run Cabal
 cabal() {
-    $CABAL $CABAL_ARGS "$@"
+    $CABAL $CABAL_ARGS_NO_CONFIG_FILE "$@"
 }
 
 die() {

cabal-install/tests/IntegrationTests/user-config/should_run/uses_CABAL_CONFIG.out

+Writing default configuration to ./my-config

cabal-install/tests/IntegrationTests/user-config/should_run/uses_CABAL_CONFIG.sh

+. ../common.sh
+
+export CABAL_CONFIG=./my-config
+cabal user-config init || die "Couldn't create config file"
+test -e ./my-config || die "Config file doesn't exist"