[SPARK-21397][BUILD]Maven shade plugin adding dependency-reduced-pom.xml to …

[zuotingbing]

…base directory

What changes were proposed in this pull request?

1. run ./build/mvn -DskipTests clean package and we get many files 'dependency-reduced-pom.xml'
   under the source directory

2. run ./build/mvn clean, the files dependency-reduced-pom.xml can not be cleaned.

As a trivial Improvement, i suggest to specify dependencyReducedPomLocation to 'target/' to store these files.

How was this patch tested?

manual tests

[AmplabJenkins]

Can one of the admins verify this patch?

[srowen]

I like the idea, but see this note: https://maven.apache.org/plugins/maven-shade-plugin/shade-mojo.html#dependencyReducedPomLocation . I'm not clear whether this has side-effects.

[zuotingbing]

@srowen Thanks for your time. I am not sure the open issue, which is mentioned in the note, whether has bean resolved. as the note said

setting a value for this parameter with a directory other than ${basedir} will change the value of ${basedir}

,but after running mvn checkstyle:check , i get the right path of ${basedir}/target/checkstyle-output.xml

[srowen]

That's not the problem this would create -- it changes basedir after execution of the shade plugin, so it might affect things like the release build. Is it really a problem? gitignore already ignores these files, even though they're a little annoying.

[zuotingbing]

I just use mvn checkstyle:check ,which contains output files with basedir, to check whether the basedir is correct with this PR.
Could you please specify the affect exactly as you said? what is your mean about release build? or does it the output package is not right?

[zuotingbing]

Yes this PR is a trivial Improvement for me. Thanks.

[srowen]

Meaning I think you'd have to run the release process to verify the artifacts still work, because it's the process that uses shading