Use STACK_YAML env var instead of relinking the file

If STACK_YAML is set to "stack.yaml" itself then we remove the file and
link it to itelf. Which is obviously incorrect. So just avoid relinking
and use the envvar.

.circleci/config.yml

@@ -89,10 +89,6 @@ preinstall: &preinstall
         # required for outbound https for stack and for stack setup
         apt-get install -y netbase xz-utils make
 
-        # If a custom stack-yaml is specified, replace the default with that
-        if test -e "$STACK_YAML"; then rm -f stack.yaml && ln -sv $STACK_YAML stack.yaml; else true; fi
-        unset STACK_YAML
-
         # Get packcheck if needed
         CURL=$(which curl)
         PACKCHECK_URL=${PACKCHECK_GITHUB_URL}/${PACKCHECK_GITHUB_COMMIT}/packcheck.sh

.github/workflows/packcheck.yml

@@ -166,9 +166,6 @@ jobs:
         sudo apt-get install -y curl
         # required for outbound https for stack and for stack setup
         sudo apt-get install -y netbase xz-utils make
-        # If a custom stack-yaml is specified, replace the default with that
-        if test -e "$STACK_YAML"; then rm -f stack.yaml && ln -sv $STACK_YAML stack.yaml; else true; fi
-        unset STACK_YAML
 
     - name: Download packcheck
       run: |

.travis.yml

@@ -206,10 +206,6 @@ install: true
 
 script:
   - |
-    # If a custom stack-yaml is specified, replace the default with that
-    if test -e "$STACK_YAML"; then rm -f stack.yaml && ln -sv $STACK_YAML stack.yaml; else true; fi
-    unset STACK_YAML
-
     # Get packcheck if needed
     CURL=$(which curl)
     PACKCHECK_URL=${PACKCHECK_GITHUB_URL}/${PACKCHECK_GITHUB_COMMIT}/packcheck.sh

packcheck.sh

@@ -376,7 +376,7 @@ show_help() {
   #help_envvar ENABLE_INSTALL "[y] DESTRUCTIVE! Install the package after building"
 
   show_step1 "stack options"
-  help_envvar STACK_YAML "Alternative stack config, cannot be a path, just the file name"
+  help_envvar STACK_YAML "Alternative stack config file path relative to project root"
   help_envvar STACK_OPTIONS "ADDITIONAL stack global options (e.g. -v) to append"
   help_envvar STACK_BUILD_OPTIONS "ADDITIONAL stack build command options to append"
 
@@ -667,6 +667,11 @@ ensure_stack() {
   fi
   require_cmd stack
 
+  # Empty STACK_YAML variable does not go well
+  if test -z "$STACK_YAML"
+  then
+    unset STACK_YAML
+  fi
   if test -n "$STACK_UPGRADE"
   then
     echo "Upgrading stack to the required version"