fix: .terraform-plan job

Closes #95 (closed)

In expression

(terraform plan $TF_PLAN_ARGS -out=${TF_DATA_DIR}/${CI_COMMIT_REF_SLUG}-${DEPLOYMENT_ENVIRONMENT}.tfplan -detailed-exitcode && exit_code=$?) || exit_code=$?

the variable exit_code is set in a sub-shell ( ( ... ) ). Because of that, if actual exit code is zero, the following script can't use it. Example:

bash-5.2$ (terraform plan $TF_PLAN_ARGS -out=123.tfplan -detailed-exitcode && exit_code=$?)

bash-5.2$ echo $exit_code

bash-5.2$

A subshell inherits the environment of the parent shell, but its exit status and environment changes (like setting variables) do not persist back to the parent shell.

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [6.4.1] - 2024-12-10
+
+### Fixed
+
+- Fixed an "integer expression expected" issue in a `.terraform-plan` job in the
+  `terraform-pipeline-base.yml` file by removing subshell `( ... )` from a command.
+
 ## [6.4.0] - 2024-12-05
 
 ### Changed