Very explicitly describe the URL dispatcher sequential search nature

[asvetlov]

aiohttp tries to match URL to web-handler in the order of resources (routes) addition.
Documentation should be very clear at this point.

For example /{name}, /info always matches to /{name}, /info router has no chance to be called.
On the opposite, /info, /{name} calls web handler for /{name} only if name!='info', inother words if /info handler didn't match.

The same is true for sub-apps; app.add_subapp('/pre', subapp) matches all /pre/* paths.

app.add_subapp('/pre', subapp)
app.add_routes('/pre/path', handler)

In the example above a handler for /pre/path is never matched.

A champion for documentation upgrade is needed. I don't know where we should put this chapter; this is a subject for discussion.

Related: #4078

[xypnox]

Hi, I would like to add the documentation for this issue.

An apt place where we can add this would be where we introduce variable routes.

[asvetlov]

Agree, please use a separate chapter next to Variable Routes.

[Dreamsorcerer]

This behaviour doesn't happen since we rewrote the routing algorithm for better performance in #7829.