By default, let Maven download Allure Command Line (fixes #141)

[TobiX]

Since this is a Maven plugin, we can reasonably expect that the user
already has configured maven correctly to reach Maven Central (or other
repositories) in some way. Therefore, instead of trying to deduce a way
to download our commandline tools from Maven settings, just ask Maven
kindly to do the download for us.

Context

Since Allure has been available from Maven Central for quite a while, it should be less of a hassle for most users to just let Maven deal with the downloading of the command line artifact. The old code is still left as-is, but only gets used if the allureDownloadUrl is specified at all.

Additionally, this drops the embedded copy of allure-commandline, which makes this plugin quite a bit lighter.

WARNING: This breaks compatibility with Allure < 2.8.0 when not specifying <allureDownloadUrl>https://dl.bintray.com/qameta/generic/io/qameta/allure/allure/%s/allure-%s.zip</allureDownloadUrl> in the plugin configuration, but I consider this a minor problem, since that version is quite old nowadays.

Checklist

• Sign Allure CLA
• Provide unit tests (existing ITs adapted to the new feature)

[baev]

So far looks good for me 👍

WARNING: This breaks compatibility with Allure < 2.8.0 when not specifying <allureDownloadUrl>https://dl.bintray.com/qameta/generic/io/qameta/allure/allure/%s/allure-%s.zip</allureDownloadUrl> in the plugin configuration, but I consider this a minor problem, since that version is quite old nowadays.

We can fix that with additional if condition, isn't?

[TobiX]

@baev Yeah. This was just the basic "works-for-me" implementation. I'm just not sure if supporting the use case "I updated the maven plugin and not the allure CLI" is really worth keeping all this backwards-compatibility code in for 😉 So I just ripped it out while developing this. But I can put it back in, no problem.

[baev]

that would be nice. From my radar 2.7.0 is widely used these days (120k+ reports generated this week)

[TobiX]

Updated to fall back to the old URL for old versions and use Maven directly for new versions.

Future enhancement idea: The groupId and artifactId of allure-cli are currently hardcoded, people might want to override that...

[TobiX]

@baev Ping? While rebasing this, I noticed that old release are downloaded from bintray, which will be shut down in the near future (https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/). Maybe it would be a good idea to push the old releases to Central and update this downloader to always fetch from there?

[baev]

@TobiX we are migrating from bintray this week, but I'm not sure yet how we are going to deal with old releases