refactor: use Go 1.22's ServeMux path patterns instead gorilla/mux

[benhoyt]

DRAFT: not yet ready for review. And I still need to figure out how this applies to snapd and run it past them.

See also: draft of using Copilot to do this in the snapd repo

Oddly, it doesn't decrease the binary size. In fact, building with the flags we use to build the snap, it's very slightly bigger (exactly 4096 = 4KB). Not sure why, maybe something's bumped it into using another 4KB "page".

In terms of performance, routing is 30% faster, and does fewer memory allocations. Not that that is a big driver here, both are at the millisecond level. But here are the numbers of this benchmark:

          │ router_gorilla.txt │         router_servemux.txt         │
          │       sec/op       │   sec/op     vs base                │
Router-16          2.699µ ± 6%   1.850µ ± 7%  -31.44% (p=0.000 n=10)

          │ router_gorilla.txt │         router_servemux.txt          │
          │        B/op        │     B/op      vs base                │
Router-16         3.406Ki ± 0%   2.574Ki ± 0%  -24.43% (p=0.000 n=10)

          │ router_gorilla.txt │        router_servemux.txt         │
          │     allocs/op      │ allocs/op   vs base                │
Router-16           31.00 ± 0%   24.00 ± 0%  -22.58% (p=0.000 n=10)

Fixes #676.

[Copilot]

Pull Request Overview

Refactors Pebble's HTTP routing from gorilla/mux to Go 1.22's native ServeMux path patterns to improve performance and reduce dependencies.

• Replaced gorilla/mux with http.ServeMux for HTTP routing
• Updated path parameter extraction from muxVars(req)["param"] to req.PathValue("param")
• Simplified path patterns to match ServeMux syntax (e.g., {task-id} to {taskID})

Reviewed Changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internals/daemon/daemon.go	Replace mux.Router with http.ServeMux and simplify route registration
internals/daemon/api.go	Remove mux dependency and update path patterns to use camelCase
internals/daemon/api_changes.go	Update parameter extraction to use req.PathValue()
internals/daemon/api_notices.go	Update parameter extraction to use req.PathValue()
internals/daemon/api_tasks.go	Update parameter extraction to use req.PathValue()
internals/daemon/daemon_test.go	Refactor tests to use HTTP requests instead of mux internals
internals/daemon/export_test.go	Remove mux-related test utilities
internals/daemon/api_test.go	Remove mux test setup and helper functions
internals/daemon/api_changes_test.go	Update tests to use req.SetPathValue()
internals/daemon/api_notices_test.go	Update tests to use req.SetPathValue()
go.mod	Remove gorilla/mux dependency
docs/specs/openapi.yaml	Update API documentation to reflect new path patterns
docs/explanation/api-and-clients.md	Update documentation examples
HACKING.md	Remove mux import from example code

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The PathPrefix field has been removed from the Command struct, but there's no clear indication of how prefix-based routing is now handled. If any commands previously used PathPrefix, this could be a breaking change.

Suggested change

	Path string
	Path string
	PathPrefix string