Get the fileHash after commit but before push

Currently in the push app flow, we get the fileHash after git push. If getting fileHash throws IOException, we don’t send back error but just log the warning since the push actually succeeded, and the fileHash is not stored back in DB.

We should instead parse the fileHash before git push, so that if it errors out, we stop git push and throw exception. This way we always get a solid fileHash in DB