The git plugin should have the option to recursively display all commits made in submodules due to updates. This will show the actual files changed and provides more useful information during a build failure.

This can be done by using 'git diff-tree' on submodule updates to determine the range of commits in a submodule update.

NOTE: I have a patch for this will provide this feature, but cannot apply it until issue 6258 is resolved. Please contact me (bvakili@oanda.com) if you'd like me to upload it.