Merge pull request #3544 from thaJeztah/carry_2740_add_config_command

Add stack config command (carry 2740)

docs/reference/commandline/index.md

@@ -152,13 +152,14 @@ read the [`dockerd`](dockerd.md) reference page.
 
 ### Swarm stack commands
 
-| Command                             | Description                                    |
-|:------------------------------------|:-----------------------------------------------|
-| [stack deploy](stack_deploy.md)     | Deploy a new stack or update an existing stack |
-| [stack ls](stack_ls.md)             | List stacks in the swarm                       |
-| [stack ps](stack_ps.md)             | List the tasks in the stack                    |
-| [stack rm](stack_rm.md)             | Remove the stack from the swarm                |
-| [stack services](stack_services.md) | List the services in the stack                 |
+| Command                             | Description                                             |
+|:------------------------------------|:--------------------------------------------------------|
+| [stack deploy](stack_deploy.md)     | Deploy a new stack or update an existing stack          |
+| [stack ls](stack_ls.md)             | List stacks in the swarm                                |
+| [stack ps](stack_ps.md)             | List the tasks in the stack                             |
+| [stack rm](stack_rm.md)             | Remove the stack from the swarm                         |
+| [stack services](stack_services.md) | List the services in the stack                          |
+| [stack config](stack_config.md)     | Output the Compose file after merges and interpolations |
 
 ### Plugin commands
 

docs/reference/commandline/stack_config.md

@@ -0,0 +1,68 @@
+---
+title: "stack config"
+description: "The stack config command description and usage"
+keywords: "stack, config"
+---
+
+# stack config
+
+```markdown
+Usage:	docker stack config [OPTIONS]
+
+Outputs the final config file, after doing merges and interpolations
+
+Aliases:
+  config, cfg
+
+Options:
+  -c, --compose-file strings   Path to a Compose file, or "-" to read from stdin
+      --orchestrator string    Orchestrator to use (swarm|kubernetes|all)
+      --skip-interpolation     Skip interpolation and output only merged config
+```
+
+## Description
+
+Outputs the final Compose file, after doing the merges and interpolations of the input Compose files.
+
+## Examples
+
+The following command outputs the result of the merge and interpolation of two Compose files.
+
+```bash
+$ docker stack config --compose-file docker-compose.yml --compose-file docker-compose.prod.yml
+```
+
+The Compose file can also be provided as standard input with `--compose-file -`:
+
+```bash
+$ cat docker-compose.yml | docker stack config --compose-file -
+```
+
+### Skipping interpolation
+
+In some cases, it might be useful to skip interpolation of environment variables.
+For example, when you want to pipe the output of this command back to `stack deploy`.
+
+If you have a regex for a redirect route in an environment variable for your webserver you would use two `$` signs to prevent `stack deploy` from interpolating `${1}`.
+
+```bash
+  service: webserver
+  environment:
+    REDIRECT_REGEX=http://host/redirect/$${1} 
+```
+
+With interpolation, the `stack config` command will replace the environment variable in the Compose file 
+with `REDIRECT_REGEX=http://host/redirect/${1}`, but then when piping it back to the `stack deploy` 
+command it will be interpolated again and result in undefined behavior. 
+That is why, when piping the output back to `stack deploy` one should always prefer the `--skip-interpolation` option.
+
+```
+$ docker stack config --compose-file web.yml --compose-file web.prod.yml --skip-interpolation | docker stack deploy --compose-file -
+```
+
+## Related commands
+
+* [stack deploy](stack_deploy.md)
+* [stack ps](stack_ps.md)
+* [stack rm](stack_rm.md)
+* [stack services](stack_services.md)

docs/reference/commandline/stack_deploy.md

@@ -111,3 +111,4 @@ axqh55ipl40h  vossibility_vossibility-collector  replicated  1/1       icecrime/
 * [stack ps](stack_ps.md)
 * [stack rm](stack_rm.md)
 * [stack services](stack_services.md)
+* [stack config](stack_config.md)