Boost: Improve 404 handler URL path processing

[haqadn]

Proposed changes:

• Improve how URL matching for static files are handled to cover more situations.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

p1739291038738559-slack-C016BBAFHHS

Does this pull request change what data or activity we track or use?

None

Testing instructions:

• On JN, the wp-content directory is not under ABSPATH. So, previously static file handlers would not work in JN.
• Enable Concatenate JS/CSS on a JN site.
• Make sure concatenated files are served from wp-content/boost-cache/static/

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add a "[Type]" label (Bug, Enhancement, Janitorial, Task).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Choose a review path based on your changes:
   • A. Team Review: add the "[Status] Needs Team Review" label
     • For most changes, including minor cross-team impacts.
     • Example: Updating a team-specific component or a small change to a shared library.
   • B. Crew Review: add the "[Status] Needs Review" label
     • For significant changes to core functionality.
     • Example: Major updates to a shared library or complex features.
   • C. Both: Start with Team, then request Crew
     • For complex changes or when you need extra confidence.
     • Example: Refactor affecting multiple systems.
3. Get at least one approval before merging.

Still unsure? Reach out in #jetpack-developers for guidance!

---

Boost plugin:

• Next scheduled release: February 13, 2025.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[github-actions]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/boost/app/lib/minify/functions-service.php	11/164 (6.71%)	0.08%	-2 💚

Full summary · PHP report · JS report

[donnchawp]

Looks good. I love that you use content_url() to build a safe url for the file.

[donnchawp]

I spoke too soon. If a URL has a directory in it, then site_url() adds the directory to dirname, which will already have the directory. For example: "/blog/blog/wp-content/boost-cache/static/"
#41743 fixes it by removing site_url() and just comparing paths.