[BEAM-2727] Make beam builds reproducible

[iemejia]

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[iemejia]

R: @kennknowles
CC: @jbonofre

[coveralls]

Changes Unknown when pulling 892fd27 on iemejia:BEAM-2727-reproducible-builds into ** on apache:master**.

[kennknowles]

Can you describe the differences to the jar? I tried a little of this a while ago and was not sure about what was OK to remove.

[iemejia]

Well the thing is that java adds timestamps in some of the jar elements, e.g. the MANIFEST file and in some cases in the files that are updated with last modification date. The plugin covers these and other cases, you can take a look at the presentation he did (is really short) for some more detail. https://zlika.github.io/presentations/devoxx_fr_2016/reproducible-builds/slides_en.html#/_pom_properties

[kennknowles]

Seems generally good to me. I mostly am concerned about the maintenance of the plugin, having a dependency, etc. And I am not so expert in Maven so it would be good to solicit feedback from e.g. @davorbonaci. But I am comfortable merging and if anything goes wrong, we just revert.

I would only want to revert the part using the reproducible build plugin, but keep the changes for javadoc and the changes to the Java test. Consider splitting the commits so we can revert just the one. But it is easy enough to manually alter the pom so I am not that worried.

[kennknowles]

Probably this should use @Rule TemporaryFolder

[iemejia]

Good idea, done.

[iemejia]

I agree with you, I have some preference for more community maintained plugins however this one makes the job and I reported one issue that was fixed and released really quickly so I think we can give it a try.
Please don't resolve/close the JIRA issue if this works because I would like still to add the JDK/maven information to the template vote. (I wonder if proposing the releaser to use the docker developer image might solve the reproduciblity issue, as well to force us to keep the docker image updated).

[coveralls]

Coverage remained the same at 69.967% when pulling b8eddd2 on iemejia:BEAM-2727-reproducible-builds into d338b44 on apache:master.

[kennknowles]

LGTM. Be sure to mention this when the next release thread comes up, as I guess if anything is going to show up as a problem, it will be in the built artifacts then.