"out" step metadata generation causes an error when build param is a WAR file

[Birdrock]

In our pipelines we specify:

build: uaa-war/uaa.war

And see this error:

fatal: cannot change to 'uaa-war/uaa.war': Not a directory

We believe this is coming from the metadata generation:

pack-concourse-resource/out

Line 104 in 422cad5

git: \"$(git -C $build rev-parse HEAD)\"

Note that the pack command and docker push do seem to work.

[bstick12]

@Birdrock Adding the git sha to the metadata isn't really necessary for the resource to function. I've removed it from the metadata in 1180c5a.

You might take a look at https://github.com/bstick12/lifecycle-build-task as it removes the need for docker in docker and uses the lifecycle directly.