Fetching repositories twice does not work

[lberki]

./compile.sh
cat > base_workspace/WORKSPACE <<EOF
git_repository(
    name = "protobuf",
    remote = "https://github.com/google/protobuf",
    commit = "HEAD"
)
EOF
cd base_workspace
../output/bazel --batch build @protobuf//:protoc
../output/bazel --batch build @protobuf//:protoc

The second execution results in an ugly exception:

java.lang.RuntimeException: Unrecoverable error while evaluating node 'GIT_CLONE:https://github.com/google/protobuf -> /usr/local/google/home/lberki/.cache/bazel/_bazel_lberki/b054b3aab4025af98dc2601e4ff14214/external/protobuf (HEAD) submodules: false' (requested by nodes 'GIT_REPOSITORY:@protobuf')
    at com.google.devtools.build.skyframe.ParallelEvaluator$Evaluate.run(ParallelEvaluator.java:745)
    at com.google.devtools.build.lib.concurrent.AbstractQueueVisitor$1.run(AbstractQueueVisitor.java:346)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.eclipse.jgit.api.errors.JGitInternalException: Destination path "protobuf" already exists and is not an empty directory
    at org.eclipse.jgit.api.CloneCommand.init(CloneCommand.java:152)
    at org.eclipse.jgit.api.CloneCommand.call(CloneCommand.java:132)
    at com.google.devtools.build.lib.bazel.repository.GitCloneFunction.compute(GitCloneFunction.java:68)
    at com.google.devtools.build.skyframe.ParallelEvaluator$Evaluate.run(ParallelEvaluator.java:709)
    ... 4 more

[damienmg]

It seems to be a git_repository specific bug. (JGit exception)

[haxorz]

we could hack around the existing file issue but, ideally, shouldn't all this external git repo stuff not happen at all in skyframe-land on the second, incremental build? why are the SkyFunction being re-executed?

[kchodorow]

Due to #251.

[haxorz]

oh, sorry, i missed the usage of "--batch". disregard my comment.

[hanwen]

I now get:

$ bazel --batch build @protobuf//:protocERROR: Error sending results to http://localhost:8082: Connection to http://localhost:8082 refused.
ERROR: no such package '@protobuf//': Invalid branch, tag, or commit: Ref HEAD can not be resolved.
INFO: Elapsed time: 35.683s

given that we ask for sha256 for files, we should probably ask for git sha1 for the commit.

[kchodorow]

HEAD is still not a recognized reference, which I think this is WAI (as generally we're not supporting "latest" as an option in WS files). commit = "<sha1>" does work and all of the other bugs mentioned in this issue have been fixed.