fix(exit code): fix the return exit code 0 if subcommand excuted failed

[donggangcj]

In fact, this error would be better resolved in the dependency library cobra and i am also trying to fix this issue of cobra.

I read the code of other projects using cobra like kubectl , github cli and these project solved this problem.
spf13/cobra#1157

I think the way that kubectl used is better. kubectl adds Run function for those commands with subcommands:
https://github.com/kubernetes/kubernetes/blob/8a3fc2d7e2043bc980bb5301d2f4292020f1a2dd/staging/src/k8s.io/kubectl/pkg/cmd/get/get.go#L155-L170

Therefore, I add empty Run function for commands with subcommands.(dependency,get,plugin,repo,search,show).Everything is ok.

Close: #8286

Signed-off-by: Dong Gang dong.gang@daocloud.io

What this PR does / why we need it:
Fix #8286
Special notes for your reviewer:

If applicable:

• this PR contains documentation
• this PR contains unit tests
• this PR has been tested for backwards compatibility

[donggangcj]

Local test results:

# Before
➜  helm git:(fix-sub-command-exit-code-error) helm repo sadd foo https://foo/bar

This command consists of multiple subcommands to interact with chart repositories.

It can be used to add, remove, list, and index chart repositories.

Usage:
  helm repo [command]

Available Commands:
  add         add a chart repository
  index       generate an index file given a directory containing packaged charts
  list        list chart repositories
  remove      remove one or more chart repositories
  update      update information of available charts locally from chart repositories

Flags:
  -h, --help   help for repo

Global Flags:
      --add-dir-header                   If true, adds the file directory to the header
      --alsologtostderr                  log to standard error as well as files
      --debug                            enable verbose output
      --kube-apiserver string            the address and the port for the Kubernetes API server
      --kube-context string              name of the kubeconfig context to use
      --kube-token string                bearer token used for authentication
      --kubeconfig string                path to the kubeconfig file
      --log-backtrace-at traceLocation   when logging hits line file:N, emit a stack trace (default :0)
      --log-dir string                   If non-empty, write log files in this directory
      ......

Use "helm repo [command] --help" for more information about a command.
➜  helm git:(fix-sub-command-exit-code-error) echo $?
0

# After
➜  helm git:(fix-sub-command-exit-code-error) bin/helm repo sadd foo https://foo/bar 
Error: "helm repo" accepts no arguments

Usage:  helm repo add|remove|list|index|update [ARGS] [flags]
➜  helm git:(fix-sub-command-exit-code-error) echo $?
1

Note, this pr will change the output from command.HelpFunc() to command.Long, I wonder if this will create other problems.

[bacongobbler]

IMO, let's see if we can get a fix upstream first before we resort to hacks/workarounds.

[donggangcj]

Indeed, we should give priority to get a fix upstream first .However, this seems to take a long time to wait.😁

[bacongobbler]

If you wish to fix the issue, please do so upstream. We're happy to wait for a fix. Rushing to implement a hack or a workaround will only result in more issues down the line.

[donggangcj]

@bacongobbler Okay， thanks!