docs: document {{#if}} / {{#else}} / {{#endif}} template syntax in instructions files

[Copilot]

Summary

Ensures the {{#if}} template conditional syntax is clearly documented for the model, prompted by the additions in #29620 which introduced {{#else}} / {{#endif}} support.

Changes

github-agentic-workflows.md

Added a new "Prompt Template Conditionals ({{#if}})" section (after the "GitHub Context Expression Interpolation" section) covering:

• Full syntax ({{#if}} / {{#else}} / {{#endif}})
• Clarification that {{#endif}} is the primary/preferred closing tag and {{/if}} is permanently supported as an alternate
• Supported condition forms (bare value, equality ==, inequality !=, strict equality ===/!==)
• Two usage examples (with and without {{#else}})
• Integration note pointing to experiments.md
• Key notes: fenced code blocks are preserved, nested conditionals are not supported, tags are stripped before the agent sees the prompt

experiments.md

Updated all code examples to use:

• {{#else}} instead of {{else}}
• {{#endif}} instead of {{/if}} (the primary closing form)

[Copilot]

Pull request overview

Documents the workflow prompt templating conditionals ({{#if}} / {{#else}} / {{#endif}}) and updates experiment documentation/examples to match the newer tag forms.

Changes:

• Added a “Prompt Template Conditionals ({{#if}})" section to clarify conditional syntax, supported operators, and usage notes.
• Updated .github/aw/experiments.md examples to use {{#else}} and {{#endif}}.
• Updated the experiment spec JSON shape in the daily attribution workflow lock file.

Show a summary per file

File	Description
.github/workflows/daily-community-attribution.lock.yml	Updates GH_AW_EXPERIMENT_SPEC to the newer { variants: [...] } schema form.
.github/aw/github-agentic-workflows.md	Adds documentation for conditional template syntax and behavior.
.github/aw/experiments.md	Refreshes examples to the new {{#else}} / {{#endif}} tag forms.

Copilot's findings

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Comments suppressed due to low confidence (1)

.github/aw/github-agentic-workflows.md:2197

• The “Notes” bullets conflict: you state tags in fenced code blocks are preserved verbatim, but then say template tags are not visible to the agent and are stripped. Also, nested conditionals are not reliably treated as literal text by the current regex-based renderer (behavior is effectively undefined). Suggest clarifying that tags are stripped only for supported, well-formed conditionals outside fenced code blocks, and that nested conditionals are unsupported/undefined (may render incorrectly or leak tags).

- **Fenced code blocks are preserved** — `{{#if}}` tags inside `` ``` `` blocks are never processed; they appear verbatim in the output.
- **Nested conditionals are not supported** — do not place `{{#if}}` inside another `{{#if}}` block; the inner tags will be treated as literal text and appear verbatim in the agent prompt.
- **Template tags are not visible to the agent** — all `{{#if}}` / `{{#else}}` / `{{#endif}}` tags are stripped from the prompt before the agent runs.

• Files reviewed: 3/3 changed files
• Comments generated: 2

[Copilot]

The truthiness semantics for the “Bare value” condition look incomplete/inaccurate vs the implementation in actions/setup/js/is_truthy.cjs: it treats (case-insensitive) "", "false", "no", "0", "null", and "undefined" as falsy. The docs currently only call out empty + "false", which could lead authors to accidentally keep blocks for values like 0/no/null.

Suggested change

	| Bare value | `{{#if experiments.flag }}` | value is non-empty and not `"false"` |
	| Bare value | `{{#if experiments.flag }}` | value is not empty and is not any of `"false"`, `"no"`, `"0"`, `"null"`, or `"undefined"` (case-insensitive) |

[Copilot]

This section says template tags are resolved at runtime and the agent “always sees the final resolved text”. In practice, renderMarkdownTemplate only removes tags for well‑formed supported patterns; malformed blocks (e.g., missing closing tag) are left unchanged, and tags inside fenced code blocks are intentionally preserved. Consider softening the wording to avoid implying tags can never reach the agent.

This issue also appears on line 2195 of the same file.

Suggested change

	The workflow markdown body supports a lightweight template language for conditional blocks. Template tags are resolved **at runtime, before the agent receives the prompt** — the agent always sees the final resolved text.
	The workflow markdown body supports a lightweight template language for conditional blocks. Supported template tags are resolved **at runtime, before the agent receives the prompt**, so the agent typically sees the rendered result; malformed tags or tags in preserved contexts may remain unchanged.