Refactor cache memory prompt to markdown template with placeholder interpolation

[Copilot]

Refactor cache memory prompt text to markdown template file

Summary:
Refactored cache memory prompt from inline generation to a markdown template file with placeholder interpolation via the substitute_placeholders.cjs script.

Changes:

• Created actions/setup/md/cache_memory_prompt.md template with __GH_AW_CACHE_DIR__ and __GH_AW_CACHE_DESCRIPTION__ placeholders
• Updated buildCacheMemoryPromptSection to use EnvVars for static values
• Modified unified_prompt_step.go to pass static env vars ONLY to substitution step (not prompt creation step)
• Added 7 unit tests for buildCacheMemoryPromptSection covering single cache, multiple caches, and edge cases
• Updated integration tests to verify correct env var placement
• Recompiled all workflow files
• Merged main branch
• All formatting and linting checks passing

Implementation:

1. Prompt Creation Step: Simply cats the template file without cache env vars

   - name: Create prompt with built-in context
     env:
       GH_AW_PROMPT: /tmp/gh-aw/aw-prompts/prompt.txt
       # NO cache env vars here - only GitHub Actions expressions
     run: |
       cat "/opt/gh-aw/prompts/cache_memory_prompt.md" >> "$GH_AW_PROMPT"

2. Substitution Step: Contains cache env vars and performs interpolation

   - name: Substitute placeholders
     env:
       GH_AW_CACHE_DIR: ${{ '/tmp/gh-aw/cache-memory/' }}
       GH_AW_CACHE_DESCRIPTION: ${{ '' }}
     with:
       script: |
         substitutePlaceholders({
           substitutions: {
             GH_AW_CACHE_DIR: process.env.GH_AW_CACHE_DIR,
             GH_AW_CACHE_DESCRIPTION: process.env.GH_AW_CACHE_DESCRIPTION
           }
         })

Testing:

• All 40 cache-related tests passing
• 7 new unit tests for buildCacheMemoryPromptSection
• Verified single default cache uses template file
• Verified multiple caches use inline generation
• Verified env vars only in substitution step
• All linters passing

Original prompt

Refactor the prompt text inserted for a cache memory as a markdown file template in actions/setup/md + template expression interpolation.

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[pelikhan]

@copilot the interpolation is done in a later step. Remove sed calls and make sure the variables are passed in tbe interpolation step

[Copilot]

@copilot the interpolation is done in a later step. Remove sed calls and make sure the variables are passed in tbe interpolation step

Done in commit 49e7fbb. Removed sed calls and updated to pass cache variables (GH_AW_CACHE_DIR, GH_AW_CACHE_DESCRIPTION) through the substitute_placeholders.cjs interpolation step. The template file is now simply cat'd at runtime, and values are interpolated in the later "Substitute placeholders" step.

[pelikhan]

@copilot substitution should only happen in the substitution step

[Copilot]

@copilot substitution should only happen in the substitution step

Fixed in commit cb90f11. Cache env vars now only appear in the "Substitute placeholders" step, not the "Create prompt" step. Static values are excluded from the prompt creation step's environment and only passed to the substitution step for interpolation.

[pelikhan]

@copilot add tests for multiple caches

[Copilot]

@copilot add tests for multiple caches

Added in commit 031354e. Created 7 unit tests for buildCacheMemoryPromptSection covering:

• Single default cache with/without description (uses template file)
• Multiple caches with mixed descriptions (uses inline content)
• Single non-default cache (uses inline content)
• Edge cases (nil config, empty caches)

All 40 cache-related tests passing.

[pelikhan]

@copilot merge main, format, lint go

[Copilot]

@copilot merge main, format, lint go

Completed in commit 4600c20. Merged origin/main, ran formatting, and fixed linting issues. All linters passing.