I think this is 1 step too much. Is this the only way to verify if a remote repository is accessible? If you need to use an explicit file instead of a directory, is it possible to use http HEAD ?

[...] 1 step too much [...]

Just to verify: are you referring to the fact that this code actually downloads a file (e.g., it could've been an HTTP HEAD request), or to the fact that the --status verifies if artifact resolution works?

In the case of the former: is a remote repository required to support an HTTP HEAD request? Could we rely on the fact that if HTTP HEAD is OK, HTTP GET will be OK, too?

It depends on what you define as "artifact resolution works". I'm not interested if the implementation is correct. I wish there's a way to only confirm that the connection works. It is about returning questions on StackOverflow that say Maven can't download things, but it is just that it cannot reach a repository. Possible rootcauses are missing proxies (or misconfigured) and misconfigured mirrors. Maybe @michael-o or @cstamas can think of a low-level reliable way to conform this.

From my experience this is not testing a random artifact which works but more enabling the aether logs which help, ultimately logging the request to be able to replay it with curl to do the check. Rest is random tests which can easily be proven false positive/negative due to proxies (correct) configuration.

The goal of this code is not to explain what is wrong and how the user should fix it. I agree with @rmannibucau that the Aether logs are more suitable for that. What this code wants to do is tell the user they have a problem, without even building a project.

Ideally, in the case of the StackOverflow questions that @rfscholte refers to, we could say "please share the output of mvn --status". Their output might look like this for example:

[INFO] Local repository setup check completed
[INFO] Connection check for repository 'corporate-repo' at 'https://pkgs.dev.azure.com/big-corporate/project/_packaging/whatever-repository/maven/v1' completed
Downloading from corporate-repo: https://pkgs.dev.azure.com/big-corporate/project/_packaging/whatever-repository/maven/v1/org/apache/maven/apache-maven/3.8.6/apache-maven-3.8.6.pom
Downloading from misconfigured-mirror: https://non-existing.example.com/maven2/org/apache/maven/apache-maven/3.8.6/apache-maven-3.8.6.pom
[INFO] Artifact resolution check completed
[INFO]
[ERROR] The following issues where found
[ERROR] 1.  Connection to misconfigured-mirror [https://non-existing.example.com/maven2/] not possible. Cause: non-existing.example.com: nodename nor servname provided, or not known
[ERROR] 2.  Could not find artifact org.apache.maven:apache-maven:pom:3.8.6 in corporate-repo (https://pkgs.dev.azure.com/big-corporate/project/_packaging/whatever-repository/maven/v1)
[ERROR] 3.  Could not transfer artifact org.apache.maven:apache-maven:pom:3.8.6 from/to misconfigured-mirror (https://non-existing.example.com/maven2/): non-existing.example.com: nodename nor servname provided, or not known

Even though this doesn't tell the user the solution, it points them in a few directions where they could look. It's a lot more compact than the complete Aether logs - which the user could still inspect, in case this message doesn't point them in the right direction already.