Add support for 'platforms' in both task and command (#980)

docs/docs/api_reference.md

@@ -139,6 +139,7 @@ includes:
 | `prefix` | `string` | | Defines a string to prefix the output of tasks running in parallel. Only used when the output mode is `prefixed`. |
 | `ignore_error` | `bool` | `false` | Continue execution if errors happen while executing commands. |
 | `run` | `string` | The one declared globally in the Taskfile or `always` | Specifies whether the task should run again or not if called more than once. Available options: `always`, `once` and `when_changed`. |
+| `platforms` | `[]string` | All platforms | Specifies which platforms the task should be run on. |
 
 :::info
 
@@ -189,6 +190,7 @@ tasks:
 | `vars` | [`map[string]Variable`](#variable) | | Optional additional variables to be passed to the referenced task. Only relevant when setting `task` instead of `cmd`. |
 | `ignore_error` | `bool` | `false` | Continue execution if errors happen while executing the command. |
 | `defer` | `string` | | Alternative to `cmd`, but schedules the command to be executed at the end of this task instead of immediately. This cannot be used together with `cmd`. |
+| `platforms` | `[]string` | All platforms | Specifies which platforms the command should be run on. |
 
 :::info
 

docs/docs/usage.md

@@ -439,6 +439,73 @@ tasks:
       - echo {{.TEXT}}
 ```
 
+## Platform specific tasks and commands
+
+If you want to restrict the running of tasks to explicit platforms, this can be achieved
+using the `platforms` key. Tasks can be restricted to a specific OS, architecture or a
+combination of both.
+
+The `build-windows` task below will run only on Windows, and on any architecture:
+
+```yaml
+version: '3'
+
+tasks:
+  build-windows:
+    platforms: [windows]
+    cmds:
+      - echo 'Running command on windows'
+```
+
+This can be restricted to a specific architecture as follows:
+
+```yaml
+version: '3'
+
+tasks:
+  build-windows-amd64:
+    platforms: [windows/amd64]
+    cmds:
+      - echo 'Running command on windows (amd64)'
+```
+
+It is also possible to restrict the task to specific architectures:
+
+```yaml
+version: '3'
+
+tasks:
+  build-amd64:
+    platforms: [amd64]
+    cmds:
+      - echo 'Running command on amd64'
+```
+
+Multiple platforms can be specified as follows:
+
+```yaml
+version: '3'
+
+tasks:
+  build-windows:
+    platforms: [windows/amd64, darwin]
+    cmds:
+      - echo 'Running command on windows (amd64) and darwin'
+```
+
+Individual commands can also be restricted to specific platforms:
+
+```yaml
+version: '3'
+
+tasks:
+  build-windows:
+    cmds:
+      - cmd: echo 'Running command on windows (amd64) and darwin'
+        platforms: [windows/amd64, darwin]
+      - cmd: echo 'Running on all platforms'
+```
+
 ## Calling another task
 
 When a task has many dependencies, they are executed concurrently. This will

docs/static/schema.json

@@ -155,6 +155,13 @@
           "run": {
             "description": "Specifies whether the task should run again or not if called more than once. Available options: `always`, `once` and `when_changed`.",
             "$ref": "#/definitions/3/run"
+          },
+          "platforms": {
+            "description": "Specifies which platforms the task should be run on.",
+            "type": "array",
+            "items": {
+              "type": "string"
+            }
           }
         }
       },
@@ -233,6 +240,13 @@
           "defer": {
             "description": "",
             "type": "boolean"
+          },
+          "platforms": {
+            "description": "Specifies which platforms the command should be run on.",
+            "type": "array",
+            "items": {
+              "type": "string"
+            }
           }
         },
         "additionalProperties": false,