add docs

docs/conditions.md

@@ -9,6 +9,7 @@ This document defines `Conditions` and their capabilities.
 - [Syntax](#syntax)
   - [Check](#check)
   - [Parameters](#parameters)
+  - [Resources](#resources)
 - [Examples](#examples)
 
 ## Syntax
@@ -57,10 +58,31 @@ only start with alpha characters and `_`. For example, `fooIs-Bar_` is a valid
 parameter name, `barIsBa$` or `0banana` are not.
 
 Each declared parameter has a type field, assumed to be string if not provided by the user. 
-The other possible type is array — useful, checking a pushed branch name doesn't match any of 
+The other possible type is array — useful, for instance, checking that a pushed branch name doesn't match any of 
 multiple protected branch names. When the actual parameter value is supplied, its parsed type 
 is validated against the type field.
 
+### Resources
+
+Conditions can declare input [`PipelineResources`](resources.md)  via the `resources` field to 
+provide the Condition container step with data or context that is needed to perform the check.
+
+Input resources, like source code (git), are dumped at path
+`/workspace/resource_name` within a mounted
+[volume](https://kubernetes.io/docs/concepts/storage/volumes/). The condition container can use the `path`
+[template](./tasks.md#Templating) key to refer to the local path to the mounted resource.
+
+```yaml
+spec:
+  resources:
+    - name: workspace
+      type: git
+  check:
+    image: alpine
+    command: ["/bin/sh"]
+    args: ['-c', 'test -f ${resources.workspace.path}/README.md']
+```
+
 ## Examples
 
 For complete examples, see

docs/pipelines.md

@@ -304,6 +304,12 @@ tasks:
       name: build-push
     conditions:
       - conditionRef: my-condition
+        params:
+          - name: my-param
+            value: my-value
+        resources:
+          - name: workspace
+            resource: source-repo
 ```
 
 In this example, `my-condition` refers to a [Condition](#conditions) custom resource. The `build-push`