Snapshot artefacts which insufficient information provided in maven-metadata.xml fail to download

[aconstantin]

In case a snapshot artefact is simply pushed in the fashion of a release artefact to a maven repository it lacks some information about the available snapshots and filenames in the maven-metadata.xml.

An example for such a case

<metadata modelVersion="1.1.0">
  <groupId>com.rbmhtechnology.example</groupId>
  <artifactId>example-docs</artifactId>
  <version>1.5-SNAPSHOT</version>
  <versioning>
    <lastUpdated>20170402093439</lastUpdated>
  </versioning>
</metadata>

A proper snapshot maven-metadata.xml would look like this

<metadata modelVersion="1.1.0">
  <groupId>com.rbmhtechnology.example</groupId>
  <artifactId>example-docs</artifactId>
  <version>0.20.0-SNAPSHOT</version>
  <versioning>
    <snapshot>
      <timestamp>20160407.074958</timestamp>
      <buildNumber>6</buildNumber>
    </snapshot>
    <lastUpdated>20160407222835</lastUpdated>
    <snapshotVersions>
      <snapshotVersion>
        <classifier>javadoc</classifier>
        <extension>jar</extension>
        <value>0.20.0-20160407.074958-6</value>
        <updated>20160407074958</updated>
      </snapshotVersion>
      <snapshotVersion>
        <classifier>sources</classifier>
        <extension>jar</extension>
        <value>0.20.0-20160407.074958-6</value>
        <updated>20160407074958</updated>
      </snapshotVersion>
      <snapshotVersion>
        <extension>jar</extension>
        <value>0.20.0-20160407.074958-6</value>
        <updated>20160407074958</updated>
      </snapshotVersion>
      <snapshotVersion>
        <extension>pom</extension>
        <value>0.20.0-20160407.074958-6</value>
        <updated>20160407074958</updated>
      </snapshotVersion>
    </snapshotVersions>
  </versioning>
</metadata>

Currently we require the latter to construct the appropriate download url for a certain classifier.

If this is not available, the apidoc server simply fails constructing the url.

This should be changed, that the fallback in such cases (lacking the required information for snapshots) is a standard release style URL.