Development questions

I'm starting to poke around and I'm thinking about contributing, but I have a few questions.
- Do you prefer a squashed commit for PRs?
- I would like to use Eclipse as my IDE, but I've hit a couple snags:
- tests/.../bugpatterns/testdata is excluded by default. Is there a way to keep it excluded (so the files don't get compiled), but still view it in the project? I would like to view/edit positive/negative test cases in Eclipse, if at all possible
- Running Eclipse's JUnit runner results in a bunch of exceptions. I'm assuming it's because eclipse's compiler is different? If I run `mvn test` everything works correctly.

```
java.lang.NoSuchFieldError: NATIVE_HEADER_OUTPUT
at com.sun.tools.javac.file.Locations.initHandlers(Locations.java:689)
at com.sun.tools.javac.file.Locations.(Locations.java:98)
at com.sun.tools.javac.util.BaseFileManager.createLocations(BaseFileManager.java:88)
at com.sun.tools.javac.util.BaseFileManager.(BaseFileManager.java:73)
at com.sun.tools.javac.nio.JavacPathFileManager.(JavacPathFileManager.java:115)
at com.google.errorprone.ErrorProneInMemoryFileManager.(ErrorProneInMemoryFileManager.java:70)
at com.google.errorprone.ErrorProneInMemoryFileManager.(ErrorProneInMemoryFileManager.java:66)
at com.google.errorprone.CompilationTestHelper.(CompilationTestHelper.java:64)
at com.google.errorprone.CompilationTestHelper.newInstance(CompilationTestHelper.java:94)
at com.google.errorprone.bugpatterns.NonnullTest.setUp(NonnullTest.java:13)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
```

```
Luna Service Release 1 (4.4.1)
Build id: 20140925-1800
Eclipse Java Development Tools
Version: 3.10.0.v20140925-0400
Build id: M20140925-0400
```

```
$ java -version
java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)
```

```
$ uname -a
Linux prowl 3.13.0-55-generic #94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
```