Mention --java_language_version and --tool_java_language_version

[g-ortuno]

Context: I just spent three days trying to build copybara in an external workspace and kept getting the following error (which is also mentioned in #221 ):

external/com_github_google_copybara/java/com/google/copybara/onboard/core/AskInputProvider.java:117: error: cannot find symbol
                    var unused = input.convert(s, resolver);
                    ^
  symbol:   class var
  location: class Mode
external/com_github_google_copybara/java/com/google/copybara/onboard/core/InputProviderResolverImpl.java:60: error: cannot find symbol
      var unused = generator.consumes();
      ^
  symbol:   class var
  location: class InputProviderResolverImpl

I realized that I needed to update my .bazelrc only after combing through the changes trying to find a clue as to how to fix the issue.

I'm pretty new to bazel external repositories, having mostly worked with blaze and Chromium's GN, but I thought mentioning this in the docs could help other developers starting with bazel.

If the fix is too obvious, feel free to ignore :)

[sin-ack]

FYI I also needed to add build --java_runtime_version=11.

[mikelalcon]

This shouldn't be needed if you keep $PROJECT_ROOT/.bazelrc that comes in the repository:

<o> [master] ~/dev/copybara$ bazel build //java/com/google/copybara:copybara_deploy.jar
Extracting Bazel installation...
Starting local Bazel server and connecting to it...
INFO: Analyzed target //java/com/google/copybara:copybara_deploy.jar (113 packages loaded, 1662 targets configured).
INFO: Found 1 target...
Target //java/com/google/copybara:copybara_deploy.jar up-to-date:
  bazel-bin/java/com/google/copybara/copybara_deploy.jar
INFO: Elapsed time: 68.812s, Critical Path: 20.05s
INFO: 303 processes: 8 internal, 208 darwin-sandbox, 87 worker.
INFO: Build completed successfully, 303 total actions

<o> [master] ~/dev/copybara$ rm .bazelrc

<o> [master] ~/dev/copybara$ bazel build //java/com/google/copybara:copybara_deploy.jar
INFO: Build options --java_language_version, --jvmopt, --test_env, and 1 more have changed, discarding analysis cache.
INFO: Analyzed target //java/com/google/copybara:copybara_deploy.jar (0 packages loaded, 1662 targets configured).
INFO: Found 1 target...
ERROR: /Users/malcon/dev/copybara/java/com/google/copybara/http/auth/BUILD:19:13: Building java/com/google/copybara/http/auth/libauth.jar (3 source files) and running annotation processors (StarlarkMethodProcessor) failed: (Exit 1): java failed: error executing command (from target //java/com/google/copybara/http/auth:auth) external/remotejdk11_macos_aarch64/bin/java -XX:-CompactStrings '--add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED' '--add-exports=jdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED' ... (remaining 16 arguments skipped)
java/com/google/copybara/http/auth/BearerInterceptor.java:41: warning: as of release 10, 'var' is a restricted local variable type and cannot be used for type declarations or as the element type of an array
      var unused = req.getHeaders().setAuthorization("Bearer " + token);
          ^
java/com/google/copybara/http/auth/BearerInterceptor.java:41: error: cannot find symbol
      var unused = req.getHeaders().setAuthorization("Bearer " + token);
      ^
  symbol:   class var
  location: class BearerInterceptor
Target //java/com/google/copybara:copybara_deploy.jar failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 10.568s, Critical Path: 7.03s
INFO: 209 processes: 11 internal, 155 darwin-sandbox, 43 worker.
FAILED: Build did NOT complete successfully
<o> [master] ~/dev/copybara$

[mikelalcon]

Ahh I see you use it as part of a workspace. Rather than recommending changing .bazelrc, that most of the users won't need, you could add a note about how to embed in a workspace? (and say to add the flags in $COPYBARA_ROOT/.bazelrc to $YOURPROJECT/.bazelrc)