Re: [PATCH v3 4/4] urlmatch: allow globbing for the URL host part

On Thu, Jan 26, 2017 at 12:43:31PM -0800, Junio C Hamano wrote:

Patrick Steinhardt [off-list ref] writes:

quoted

The URL matching function computes for two URLs whether they match not.
The match is performed by splitting up the URL into different parts and
then doing an exact comparison with the to-be-matched URL.

The main user of `urlmatch` is the configuration subsystem. It allows to
set certain configurations based on the URL which is being connected to
via keys like `http.<url>.*`. A common use case for this is to set
proxies for only some remotes which match the given URL. Unfortunately,
having exact matches for all parts of the URL can become quite tedious
in some setups. Imagine for example a corporate network where there are
dozens or even hundreds of subdomains, which would have to be configured
individually.

This commit introduces the ability to use globbing in the host-part of
the URLs. A user can simply specify a `*` as part of the host name to
match all subdomains at this level. For example adding a configuration
key `http.https://*.example.com.proxy` will match all subdomains of
`https://example.com`.

This is probably a useful improvement.

Having said that, when I mentioned "glob", I meant to also support
something like this:

	https://www[1-4].ibm.com/

The problem with additional extended syntax like proposed by you
is that we would indeed need an escaping mechanism here. '[]' are
already allowed inside the host part to enable IPv6 hosts of the
form 'https://[2001:0db8:]/', so the syntax is now ambiguous. So
we have to be cautios which characters to enable for globbing
syntax. As of now, I think we can only safely include '*' and '?'
here without escaping mechanisms.

If additional use cases come up we might still extend the syntax
later on to allow for more special syntax.

And when people read "glob", that is what they expect.

So calling this "the ability to use globbing" is misleading.
The last paragraph in the log message above needs a bit of
tweaking, perhaps like this:

	Allow users to write an asterisk '*' in place of any 'host'
	or 'subdomain' label as part of the host name.  For example,
	"http.https://*.example.com.proxy" sets "http.proxy" for all
	direct subdomains of "https://example.com",
	e.g. "https://foo.example.com", but not
	"https://foo.bar.example.com".

Fortunately, your update to config.txt, which is facing the end
users, does not misuse the word and instead is explicit that the
only thing the matcher does is to match '*' to a single hierarchy.
It is clear that even http://www*.ibm.com/ is not supported from
the description, which is good.

I agree that globbing is the wrong word here. I'll swap in
"wildcard" where applicable.

I'll send a version 4 later on. Thanks again for your feedback
and improvements.

Regards
Patrick