Fix Default App Directory

[hone]

per lifecycle#77 the default app directory shouldn't be prefixed with /app

[jkutner]

i don't know why, but when i pull this branch locally, i see:

$ git diff master..fix-default-app-directory
...
@@ -419,8 +403,7 @@ func (b *BuildConfig) build(ctx context.Context, lifecycle *build.Lifecycle) err
                "builder",
                build.WithArgs(
                        "-buildpacks", buildpacksDir,
-                       "-layers", layersDir,
-                       "-app", appDir,
+                       "-layers", launchDir,
                        "-group", groupPath,
                        "-plan", planPath,
                        "-platform", platformDir,

unsure why Github doesn't show that for me

[jkutner]

i think it just needs a rebase

[sclevine]

@ekcasey I see some other places that reference /workspace/app or look like they might need to be updated for the directory rename: https://github.com/buildpack/pack/blob/master/build.go#L77

[hone]

my bad, the rebase fixed it locally for me. sorry :( going to close this.

[ekcasey]

@sclevine probably shouldn't have put buildpacks/lifecycle#77 in done. The lifecycle changes are done which was higher priority b/c we wanted to finish lifecycle beta first so that folks could create their beta builders.

More work need to be done to allow pack to use the new defaults. We need to create a second volume for the app. Until that is done pack need to use the flags to explicitly set values to the original default.