Add clear-caches directive for reducing Docker image sizes

[Copilot]

Implementation Plan for clear-caches Feature

• Add ClearCachesDirective type to aptfile package
• Add parser function parseClearCachesDirective in aptfile/main.go
• Update ParseLine switch statement to handle "clear-caches" directive
• Add test case for clear-caches parsing in aptfile/main_test.go
• Implement clearCaches function in main.go to run apt-get clean and remove cache directories
• Add case in processAptfile to handle ClearCachesDirective
• Defer clear-caches execution to run after packages are installed
• Test the implementation with sample Aptfiles
• Update documentation in README.md
• Fix clear-caches to run only once even if multiple directives exist
• Fix glob expansion in rm command by using sh -c
• Run code security checks (CodeQL - no issues found)
• All tests passing
• Fix unrelated CI GoReleaser build failure by adding --snapshot --clean flags

Summary

Successfully implemented the clear-caches directive feature and fixed the unrelated CI build issue with GoReleaser that was failing because it expected a git tag on non-release builds.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Ability to clear caches at the end of installation</issue_title>
<issue_description>It would be helpful to be able to have some directive like

clear-caches

at the end of the Aptfile, so as to delete cache directories (commonly done in Dockerfiles to reduce image sizes).</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Ability to clear caches at the end of installation #4

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[ericsuh]

@copilot please fix the test failure in CI, even though it is not related to this PR's changes.

[Copilot]

@copilot please fix the test failure in CI, even though it is not related to this PR's changes.

Fixed the GoReleaser CI failure by adding --snapshot --clean flags to the build command. This allows GoReleaser to build without requiring a git tag, which is appropriate for CI builds on PRs. (commit 13cf2e8)

[Copilot]

Pull request overview

Adds a new clear-caches Aptfile directive to reduce final image/disk footprint by cleaning apt caches after all package installation has completed, aligning with common Docker optimization patterns.

Changes:

• Add clear-caches directive parsing in aptfile (no args/options).
• Defer cache-clearing execution in processAptfile until after installPackages.
• Document the directive in the README and add a parser unit test.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

File	Description
main.go	Collects clear-caches directives during parsing and runs a new clearCaches() step after installs.
aptfile/main.go	Introduces ClearCachesDirective and parsing logic for clear-caches.
aptfile/main_test.go	Adds a ParseLine unit test case for the new directive.
README.md	Documents clear-caches usage in the example Aptfile.

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[Copilot]

clearCachesDirectives is only used as a presence check (len(...) > 0) and the directive struct is empty, so storing every occurrence is unnecessary. Consider replacing this slice with a simple boolean (e.g., clearCachesRequested) to better express intent and avoid redundant allocations/append calls.

[Copilot]

New clear-caches behavior (deferral until after installPackages and idempotent execution) isn’t covered by tests. Since this file already has unit tests, add a test that runs processAptfile(..., dryRun=true) (or calls clearCaches(true)) while capturing stdout/stderr to assert the directive is executed exactly once and only after the install step.