Better error message on class uniqueness lock file failure

[CRogers]

Before this PR

Trying to diagnose a problem with an internal project where circle says that checkClassUniqueness but locally checkClassUniqueness --write-locks does nothing. Very hard to diagnose as it doesn't show the expected difference. Currently looks like:

baseline-class-uniqueness.lock is out of date, please run `./gradlew checkClassUniqueness --write-locks` to update this file

After this PR

==COMMIT_MSG==
When checkClassUniqueness fails, it will show the difference between the actual and expected lock file.
==COMMIT_MSG==

This will make it easier to debug. Now looks like:

baseline-class-uniqueness.lock is out of date, please run `./gradlew checkClassUniqueness --write-locks` to update this file. The diff moving from on disk to what baseline expects is:
  
  --- on disk
  +++ expected
  @@ -1,1 +1,32 @@
  -blah
  +# Danger! Multiple jars contain identically named classes. This may cause different behaviour depending on classpath ordering.
  +# Run ./gradlew checkClassUniqueness --write-locks to update this file
  +
  +## runtimeClasspath
  +[javax.el:javax.el-api, javax.servlet.jsp:jsp-api]
  +  - javax.el.ArrayELResolver
  +  - javax.el.BeanELResolver
  +
  
  On disk was:
  
  blah
  
  Expected was:
  # Danger! Multiple jars contain identically named classes. This may cause different behaviour depending on classpath ordering.
  # Run ./gradlew checkClassUniqueness --write-locks to update this file
  
  ## runtimeClasspath
  [javax.el:javax.el-api, javax.servlet.jsp:jsp-api]
    - javax.el.ArrayELResolver
    - javax.el.BeanELResolver

Possible downsides?

None I can think of.

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Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

When checkClassUniqueness fails, it will show the difference between the actual and expected lock file.

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[svc-autorelease]

Released 3.35.0