#159 Refactor NonReversibleValidationException package

[ignite1771]

Description

Categorize NonReversibleValidationException.java into exception package and solve related build dependencies.
To avoid bazel cycle in dependency graph error as a result, I found the root cause is the java doc so I modify it a little bit tricky.

/**
- * Exception thrown when a {@link Transformation} is not reversible but the configuration asked for
+ * Exception thrown when a {@link com.google.copybara.Transformation} is not reversible but the configuration asked for
...
*/

Motivation and Context

All exception classes should be categorized into the exception package. By doing so, the source code would have better modularity.
This PR solves #159

How has this been tested?

Have passed Bazel build completely successfully and not affected functionalities.

Types of changes

Refactor

Checklist:

• I have read the CONTRIBUTING doc
• I have signed the Google Individual CLA
• My code follows Google Java Style Guide.

[ignite1771]

@mikelalcon
I've implemented the proposed solution to the issue mentioned few days ago #159 :)

Any pointers would be greatly appreciated. Thanks!

[ignite1771]

I have just rebased on the updates after this PR opened 1358d8a :)

[ignite1771]

Hi! Just want to check,
should I rebase on newest updates or squash commits,
on current condition that "Change imported to the internal review system" ?
Thanks :)

[ignite1771]

@mikelalcon
I found the instructions in #79 (comment)
so I just squashed commits and rebased on the newest updates :)

Any pointers would be greatly appreciated. Thanks!

[hsudhof]

Hi, apologies for the slow turnaround. Essentially this requires some manual attention from our side because it breaks some of our custom extensions. We will get to it ASAP.

[ignite1771]

Hi, apologies for the slow turnaround. Essentially this requires some manual attention from our side because it breaks some of our custom extensions. We will get to it ASAP.

I just made a experiment whether internal checks failed is because that, CheckStyle "CustomImportOrder" is violated, for example:

// WRONG: violated "CustomImportOrder"
- import com.google.copybara.NonReversibleValidationException;
+ import com.google.copybara.exception.NonReversibleValidationException;
import com.google.copybara.TransformWork;
import com.google.copybara.Transformation;
import com.google.copybara.WorkflowOptions;
import com.google.copybara.exception.ValidationException;

// CORRECT: should be in this sorting order
- import com.google.copybara.NonReversibleValidationException;
import com.google.copybara.TransformWork;
import com.google.copybara.Transformation;
import com.google.copybara.WorkflowOptions;
+ import com.google.copybara.exception.NonReversibleValidationException;
import com.google.copybara.exception.ValidationException;

But it seems that it's not the root cause and still failed.
Not sure if this can provide you some ideas.
Thanks :)

[hsudhof]

No, it is not something you can fix, apologies for the delay.