Merge commit '9b0050e9aabe4be65c78ccf292a348f309d50ccd' as 'docs'

```
git subtree add --prefix=docs/ https://github.com/gohugoio/hugoDocs.git master --squash
```

Closes #11925

docs/content/en/functions/templates/Exists.md

@@ -0,0 +1,27 @@
+---
+title: templates.Exists
+description: Reports whether a template file exists under the given path relative to the layouts directory.
+categories: []
+keywords: []
+action:
+  aliases: []
+  related: []
+  returnType: bool
+  signatures: [templates.Exists PATH]
+aliases: [/functions/templates.exists]
+---
+
+A template file is any file within the `layouts` directory of either the project or any of its theme components.
+
+Use the `templates.Exists` function with dynamic template paths:
+
+```go-html-template
+{{ $partialPath := printf "headers/%s.html" .Type }}
+{{ if templates.Exists ( printf "partials/%s" $partialPath ) }}
+  {{ partial $partialPath . }}
+{{ else }}
+  {{ partial "headers/default.html" . }}
+{{ end }}
+```
+
+In the example above, if a "headers" partial does not exist for the given content type, Hugo falls back to a default template.

docs/content/en/functions/templates/_index.md

@@ -0,0 +1,13 @@
+---
+title: Template functions
+linkTitle: templates
+description:
+categories: []
+keywords: []
+menu:
+  docs:
+    identifier: templates-functions
+    parent: functions
+---
+
+Use these functions to query the template system.