feat: make suffix configurable (#10)

[schroedan]

Closes #10

[Copilot]

Pull request overview

This PR implements issue #10 by making the “file reference” environment-variable suffix configurable (defaulting to _FILE) so users can choose alternatives like __FILE.

Changes:

• Add support for FILEENV_SUFFIX and pass the configured suffix into environment resolution logic.
• Update documentation to describe FILEENV_SUFFIX and clarify default/override behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
README.md	Documents new configuration option FILEENV_SUFFIX and updates behavior notes accordingly.
main.go	Introduces config loading for the suffix and uses it when detecting and resolving *_FILE-style variables.

Suppressed comments (1)

main.go:116

• excludeEnvVar and includeEnvVar are referenced here but are not defined anywhere in the repo, which will prevent the project from compiling.

func isControlVar(key string) bool {
	switch key {
	case suffixEnvVar, excludeEnvVar, includeEnvVar:
		return true

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

Suppressed comments (1)

README.md:185

• These behavior bullets still describe _FILE-specific semantics, but the suffix is now configurable. As written, FOO_FILE/_FILE are only correct for the default suffix; for non-default suffixes the “wins” and “empty variable name” rules still apply but for FOO<suffix> / <suffix>.

- The suffix is `_FILE` by default; override it with `FILEENV_SUFFIX` (see
  [Configuration](#configuration)).
- If both `FOO` and `FOO_FILE` are set, `FOO_FILE` wins and overwrites `FOO`.
- Empty variable names (i.e. a variable literally named `_FILE`) are ignored.