Option for using the Pivotal build server should be clarified a bit more

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Under the https://docs.microsoft.com/en-us/cli/azure/ext/spring-cloud/spring-cloud/app/deployment?view=azure-cli-latest#ext_spring_cloud_az_spring_cloud_app_deployment_create-examples section, the first option (where there is no path to a JAR/ZIP package provided) can use some clarification. If you are not careful about the current folder, this command can have undesirable results:
1. If the current folder has many sub-folders the process takes forever and consumes all the CPU on your machine as it tries to create the massive TAR ball. It is not clear if it eventually succeeds because I've eventually realized my mistake and killed the command.
2. If the current folder has something that has few sub-folders but is not valid code, the deployment slot can become unusable and prevents further deployments unless it is deleted.

The ask to put some warning/awareness around the current folder structure and purpose of this option. One (mistakenly) usage of this command is to create an 'empty' staging deployment slot and the workaround is to use a dummy JAR/ZIP file of an empty Spring Boot or Steeltoe application and then use the second option instead.

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* ID: 1e7271fb-c9a5-a6ad-6dbf-30a12eb3d357
* Version Independent ID: 8772d62f-3072-4267-a25e-8547500470e3
* Content: [az spring-cloud app deployment](https://docs.microsoft.com/en-us/cli/azure/ext/spring-cloud/spring-cloud/app/deployment?view=azure-cli-latest#ext_spring_cloud_az_spring_cloud_app_deployment_create-examples)
* Content Source: [latest/docs-ref-autogen/ext/spring-cloud/spring-cloud/app/deployment.yml](https://github.com/MicrosoftDocs/azure-docs-cli/blob/master/latest/docs-ref-autogen/ext/spring-cloud/spring-cloud/app/deployment.yml)
* GitHub Login: @rloutlaw
* Microsoft Alias: **routlaw**