Feature Request: Automatic HEAD request handling

从路由注册入口 e.GET() 开始，并将其与提议的 middleware.AutoHead() 方法进行比较。检查现有的路由器和路由注册行为，然后确定在不存在显式 HEAD 路由时，自动 HEAD 处理应如何工作。完成的标准是：GET 路由能够处理 HEAD 请求并省略响应体，同时不改变显式 HEAD 的行为。

Currently, Echo requires explicit HEAD route registration for every GET route. Some other frameworks like Fiber, Express and Fastify handle this automatically. According to HTTP semantics, HEAD should behave identically to GET except that the response body is omitted. Automatically supporting HEAD for GET routes aligns with this expectation and reduces boilerplate.

Related: #654

Proposal

Add automatic HEAD handling for GET routes when no explicit HEAD route is registered.

Implementation Options

Option 1: Middleware approach

e := echo.New()
e.Use(middleware.AutoHead())

Pros:

• Opt-in
• No changes to core routing
• Simple implementation

Cons:

• Must be registered last in the middleware chain. Otherwise, middlewares registered after it will not execute for HEAD requests, since the middleware directly invokes the handler and bypasses the remaining chain

I've already implemented this approach, but after testing I realized the middleware ordering requirement makes it less convenient and more error-prone.

Option 2: Core integration

Auto-register HEAD routes during e.GET() calls, controlled by config :

e := echo.New()
e.AutoHead = true

Default value could remain false to avoid breaking existing behavior.

Pros:

• No middleware ordering constraints
• Slightly better performance, since re-routing is avoided

Cons:

• Requires changes to core Echo router/route registration

Questions

1. Would the Echo team be interested in this functionality?
2. If so, which implementation approach would be preferred: middleware or core integration? Would you consider a PR for either approach?