Added the functionality for persistent functions to chain
from root to child in the case of PersistentPreRun and
from child to root in the case of PersistentPostRun.
Added a global internal variable useChainHooks which decides
whether to use chain feature, or use the previous logic of nearest
defined ancestor.
This variable useChainHooks is disabled by default in this commit.
Developers importing the cobra package can enable it using the
function EnableChainHooks() or disable it using DisableChainHooks().
However, these functions may be called only once externally, preferably
in the init of the developers main program.
PreRunChain functions run in the order of root to child.
PostRunChain functions run in the order of child to root.
The overall exection order for a command is
PreRunChain
PersistentPreRun
PreRun
Run
PostRun
PersistentPostRun
PostRunChain
The following gist describes the usage and functionality
https://gist.github.com/algrebe/23cc8bf4739a129a6d0d
An example from the kubernetes project, for the `kubectl config`
command, which as subcommands, and flags, and all sorts of stuff, it
will generate markdown like so:
config modifies .kubeconfig files
config modifies .kubeconfig files using subcommands like "kubectl config set current-context my-context"
```
kubectl config SUBCOMMAND
```
```
--envvar=false: use the .kubeconfig from $KUBECONFIG
--global=false: use the .kubeconfig from /home/username
-h, --help=false: help for config
--kubeconfig="": use a particular .kubeconfig file
--local=false: use the .kubeconfig in the current directory
```
```
--alsologtostderr=false: log to standard error as well as files
--api-version="": The API version to use when talking to the server
-a, --auth-path="": Path to the auth info file. If missing, prompt the user. Only used if using https.
--certificate-authority="": Path to a cert. file for the certificate authority.
--client-certificate="": Path to a client key file for TLS.
--client-key="": Path to a client key file for TLS.
--cluster="": The name of the kubeconfig cluster to use
--context="": The name of the kubeconfig context to use
--insecure-skip-tls-verify=false: If true, the server's certificate will not be checked for validity. This will make your HTTPS connections insecure.
--log_backtrace_at=:0: when logging hits line file:N, emit a stack trace
--log_dir=: If non-empty, write log files in this directory
--log_flush_frequency=5s: Maximum number of seconds between log flushes
--logtostderr=true: log to standard error instead of files
--match-server-version=false: Require server version to match client version
--namespace="": If present, the namespace scope for this CLI request.
--password="": Password for basic authentication to the API server.
-s, --server="": The address and port of the Kubernetes API server
--stderrthreshold=2: logs at or above this threshold go to stderr
--token="": Bearer token for authentication to the API server.
--user="": The name of the kubeconfig user to use
--username="": Username for basic authentication to the API server.
--v=0: log level for V logs
--validate=false: If true, use a schema to validate the input before sending it
--vmodule=: comma-separated list of pattern=N settings for file-filtered logging
```
* [kubectl](kubectl.md) - kubectl controls the Kubernetes cluster manager
* [kubectl config set](kubectl_config_set.md) - Sets an individual value in a .kubeconfig file
* [kubectl config set-cluster](kubectl_config_set-cluster.md) - Sets a cluster entry in .kubeconfig
* [kubectl config set-context](kubectl_config_set-context.md) - Sets a context entry in .kubeconfig
* [kubectl config set-credentials](kubectl_config_set-credentials.md) - Sets a user entry in .kubeconfig
* [kubectl config unset](kubectl_config_unset.md) - Unsets an individual value in a .kubeconfig file
* [kubectl config use-context](kubectl_config_use-context.md) - Sets the current-context in a .kubeconfig file
* [kubectl config view](kubectl_config_view.md) - displays merged .kubeconfig settings or a specified .kubeconfig file.
