content: Add Site.IsDefault

Author: jmooring

content/en/methods/site/IsDefault.md

@@ -0,0 +1,58 @@
+---
+title: IsDefault
+description: Reports whether the given site is the default site across all dimensions.
+categories: []
+keywords: []
+params:
+  functions_and_methods:
+    returnType: bool
+    signatures: [SITE.IsDefault]
+---
+
+## Use case
+
+This method is useful to ensure that a block of code executes only once per [project](g) build, regardless of the number of [sites](g) generated by your [dimensions](g).
+
+## Default site identification
+
+The default site occupies the primary position within your multidimensional content matrix. Hugo identifies this site by selecting the first value from each dimension based on the following priority.
+
+1. [Language](g) by the lowest [weight](g) or by lexicographical order if weights are tied or undefined.
+1. [Role](g) by the lowest weight or by lexicographical order if weights are tied or undefined.
+1. [Version](g) by the lowest weight or by the first version when sorted semantically in descending order if weights are tied or undefined.
+
+## Example
+
+If you are generating a global search index or a single sitemap for a project containing multiple languages and versions, wrap that logic in an [`if`][] statement using this function. This prevents the index from being overwritten or redundantly processed for every dimensional variation.
+
+[`if`]: /functions/go-template/if/
+
+The following configuration defines a matrix of sites across language and version dimensions.
+
+{{< code-toggle file=hugo >}}
+[languages.en]
+languageCode = 'en-US'
+languageDirection = 'ltr'
+languageName = 'English'
+weight = 1
+
+[languages.de]
+languageCode = 'de-DE'
+languageDirection = 'ltr'
+languageName = 'Deutsch'
+weight = 3
+
+[versions.'v1.0.0']
+[versions.'v2.0.0']
+[versions.'v3.0.0']
+{{< /code-toggle >}}
+
+In your templates, use the following logic to restrict code execution to the default site only.
+
+```go-html-template
+{{ if hugo.IsDefault }}
+  ...
+{{ end }}
+```
+
+In this setup, the code block is only executed for the English version v3.0.0 site. English is selected because it has the lowest weight, and version v3.0.0 is selected because it is the first version when sorted semantically in descending order.