Fix: files with _snippets in their name incorrectly treated as snippet-only files

[Copilot]

Substring matching on "_snippets" caused files like top_snippets.md to be classified as SnippetFile (excluded from normal processing) instead of regular MarkdownFile.

Changes

• MarkdownFileFactory.cs: Replace relativePath.Contains("_snippets") with path-component-aware check — requires _snippets to be a directory segment, not a substring of a filename
• IncludeBlock.cs: Same fix for include validation — splits on path separators and checks for exact component match instead of IndexOf("_snippets")
• MockFileSystemExtensions.cs: Fix test helper's Contains("_snippet") (note: missing trailing s) which had the same over-matching behavior when generating docset YAML TOC entries

// Before — matches top_snippets.md, path/to/top_snippets/file.md, etc.
if (relativePath.Contains("_snippets"))

// After — only matches when _snippets is an actual directory component
if (relativePath.Contains($"{Path.DirectorySeparatorChar}_snippets{Path.DirectorySeparatorChar}")
    || relativePath.StartsWith($"_snippets{Path.DirectorySeparatorChar}"))

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Build fails when filename contains _snippets</issue_title>
<issue_description>Files with _snippets in the filename (e.g. top_snippets.md) cause build failures, presumably because the build logic treats any path containing _snippets as an include-only snippets directory.

Expected behavior

Only _snippets/ directories should be treated specially, not files that happen to contain _snippets in their name.

Workaround

Rename files to kebab case (e.g. top-snippets.md).

Reference

• elastic/elasticsearch@73c9d59</issue_description>

<agent_instructions>I think the easiest would be to detect the snippets folder using /_snippets </agent_instructions>

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

@reakaleek I guess the easiest would be to change the detection to `/_snippets`

• Fixes Build fails when filename contains _snippets #2742

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.