File dependency docs (#2408)

* WIP - File dependency docs

* Mark the old enable provider cache config as deprecated in favor of env

* explicitly call out DAG generators

* Update file-dependencies.md

* Update file-dependencies.md

Platform agnostic language

Author: ZachGoldberg

docs/2.0/docs/pipelines/guides/file-dependencies.md

@@ -0,0 +1,15 @@
+# Running Pipelines for Changes to non-IaC file dependencies
+
+Pipelines runs plan/applies based on changes to your units in your IaC repository. Intuitively, if you make a change to `path/to/my/unit/terragrunt.hcl` then Pipelines will run plan/apply in `/path/to/my/unit`.  Pipelines also supports running `run-all` when [consolidation](/2.0/reference/pipelines/configurations-as-code/api#consolidate_added_or_changed) is enabled.
+
+However, there are some cases where you may want to run Pipelines for changes to files that are not part of your IaC. For example, you may have a `terragrunt.hcl` file that imports data from a `tags.yaml` file. If you make a change to the `tags.yaml` file, you may want to run Pipelines to plan/apply the changes to the associated `terragrunt.hcl` file.  This page documents how to configure pipelines to automatically run `plan/apply` when only these data files are changed.
+
+## Configuration
+
+Pipelines will automatically detect, based on git commit history, when data files have changed and emit a `FileChanged` change. This will create a new execution in your CI flow that will invoke Terragrunt with the [`queue-include-units-reading`](https://terragrunt.gruntwork.io/docs/reference/cli-options/#queue-include-units-reading) option set to the files that have changed. Terragrunt will then scan your code for units that depend on the changed files and add them to the plan/apply.
+
+Note that Terragrunt will only be able to determine which units read the data file if that file is read using a built-in function such as `read_terragrunt_config` or is in a `include`, `dependency`, or `dependencies` block. You may want to use the [`mark_as_read`](https://terragrunt.gruntwork.io/docs/reference/built-in-functions/#mark_as_read) function to explicitly ensure that Terragrunt knows to include your unit when a particular data file is changed.
+
+## Example
+
+Here's an example of how to configure pipelines to automatically run `plan/apply` when only these data files are changed.

docs/2.0/reference/pipelines/configurations.md

@@ -89,22 +89,6 @@ pipelines:
 </HclListItemExample>
 </HclListItem>
 
-#### enable-terragrunt-provider-cache
-
-<HclListItem name="enable-terragrunt-provider-cache" requirement="optional" type="boolean">
-<HclListItemDescription>
-Enables the <span class="external-link"><a href="https://terragrunt.gruntwork.io/docs/features/provider-cache/">Terragrunt Provider Cache</a></span> for plans and applies.
-</HclListItemDescription>
-<HclListItemDefaultValue defaultValue="false"/>
-<HclListItemExample>
-
-```yaml
-pipelines:
-  enable-terragrunt-provider-cache: true
-```
-
-</HclListItemExample>
-</HclListItem>
 
 #### env
 
@@ -194,6 +178,25 @@ pipelines:
 
 ## Deprecated Configuration Options
 
+#### enable-terragrunt-provider-cache
+
+<HclListItem name="enable-terragrunt-provider-cache" requirement="optional" type="boolean">
+<HclListItemDescription>
+Enables the <span class="external-link"><a href="https://terragrunt.gruntwork.io/docs/features/provider-cache/">Terragrunt Provider Cache</a></span> for plans and applies.
+
+This option is deprecated in favor of setting `TERRAGRUNT_PROVIDER_CACHE` as an [`env`](#env) option.
+</HclListItemDescription>
+<HclListItemDefaultValue defaultValue="false"/>
+<HclListItemExample>
+
+```yaml
+pipelines:
+  enable-terragrunt-provider-cache: true
+```
+
+</HclListItemExample>
+</HclListItem>
+
 #### cli-version
 
 <HclListItem name="cli-version" requirement="deprecated" type="string">

sidebars/docs.js

@@ -314,6 +314,11 @@ const sidebar = [
         type: "doc",
         id: "2.0/docs/pipelines/guides/running-drift-detection",
       },
+      {
+        label: "File Dependencies",
+        type: "doc",
+        id: "2.0/docs/pipelines/guides/file-dependencies",
+      },
       {
         label: "Leveraging advanced Terragrunt Features",
         type: "doc",