GEODE-5804: Improve checkPom task

[PurelyApplied]

• Add updateExpectedPom task to perform copy of actual to expected.

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[rhoughton-pivot]

Why does the expected file need to exist in order to update/place. We could use this task to generate the baseline for a newly-minted module.

[PurelyApplied]

I suppose it doesn't!

[PurelyApplied]

I had been poking at it to make sure it's still good. I was getting some strange behavior where ./gradlew uEP updates the assembly pom with

diff --git a/geode-assembly/src/test/resources/expected-pom.xml b/geode-assembly/src/test/resources/expected-pom.xml
index 3f8abf5e57..b22bc8f393 100644
--- a/geode-assembly/src/test/resources/expected-pom.xml
+++ b/geode-assembly/src/test/resources/expected-pom.xml
@@ -20,7 +20,7 @@
   <groupId>org.apache.geode</groupId>
   <artifactId>apache-geode</artifactId>
   <version>1.8.0-SNAPSHOT</version>
-  <packaging>pom</packaging>
+  <packaging>tgz</packaging>
   <name>Apache Geode</name>
   <description>Apache Geode provides a database-like consistency model, reliable transaction processing and a shared-nothing architecture to maintain very low latency performance with high concurrency processing</description>
   <url>http://geode.apache.org</url>

It had been the dependency block I'd messed with to make sure I hadn't broken checkPom, so I don't know if there is just some dirty artifact there. Need to play with it a little more.

[PurelyApplied]

It seems like the actual checkPom task is only examining <dependency> blocks and not any other data. So, on the one hand, the existing behavior was "copy the actual pom to the expected pom" is what's happening, but a developer will then need to examine which difference should actually be added to their commit.

So that's strange and we should decide if checkPom should also be checking, for instance, the <packaging> for consistency. Or decide that what goes into a diff is just developer responsibility.