Help for 'cf push' is misleading: app name is not required

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• [x] I reviewed open and closed github issues that may be related to my problem.
• [x] I tried updating to the latest version of the CF CLI to see if it fixed my problem.
• [ ] ~I attempted to run the command with CF_TRACE=1 to help debug the issue.~
• [x] I am reporting a bug that others will be able to reproduce.

Describe the bug and the command you saw an issue with

The output of cf push --help indicates that APP_NAME is a required argument:

$ cf --version
cf version 8.0.0+e8d41cf8e.2021-09-16
$ cf push --help
NAME:
   push - Push a new app or sync changes to an existing app

USAGE:
   cf push APP_NAME [-b BUILDPACK_NAME]
   [-c COMMAND] [-f MANIFEST_PATH | --no-manifest] [--no-start] [--no-wait] [-i NUM_INSTANCES]
   [-k DISK] [-m MEMORY] [-p PATH] [-s STACK] [-t HEALTH_TIMEOUT] [--task TASK]
   [-u (process | port | http)] [--no-route | --random-route]
   [--var KEY=VALUE] [--vars-file VARS_FILE_PATH]...
 
   cf push APP_NAME --docker-image [REGISTRY_HOST:PORT/]IMAGE[:TAG] [--docker-username USERNAME]
   [-c COMMAND] [-f MANIFEST_PATH | --no-manifest] [--no-start] [--no-wait] [-i NUM_INSTANCES]
   [-k DISK] [-m MEMORY] [-p PATH] [-s STACK] [-t HEALTH_TIMEOUT] [--task TASK]
   [-u (process | port | http)] [--no-route | --random-route ]
   [--var KEY=VALUE] [--vars-file VARS_FILE_PATH]...

This is confusing: I coded my automation around the fact that I have to give the APP_NAME instead of it being taken from the manifest.

I then tried to leave out the APP_NAME while pushing my manifest and it worked perfectly.

I would propose to update the help to indicate that APP_NAME is not mandatory.

Provide more context

cf version 8.0.0+e8d41cf8e.2021-09-16

$ cf target
API endpoint:   https://api.cf.sap.hana.ondemand.com
API version:    3.103.0