hugo-theme-relearn/layouts/partials/favicon.html

    {{- $assetBusting := partialCached "assetbusting.hugo" . }}
    {{- $faviconMatch := false }}
    {{- $svg := dict "ext" "svg" "type" "type=\"image/svg+xml\"" }}
    {{- $png := dict "ext" "png" "type" "type=\"image/png\"" }}
    {{- $ico := dict "ext" "ico" "type" "type=\"image/x-icon\" sizes=\"any\"" }}
    {{- $faviconTypes := slice $svg $png $ico }}
    {{- $faviconNames := slice "favicon" "logo" }}
    {{- range $faviconNames }}
      {{- $faviconName := . }}
      {{- range $faviconTypes }}
        {{- if fileExists (printf "/static/images/%s.%s" $faviconName .ext) }}
          {{- $faviconMatch = true }}
    <link href="{{ printf "images/%s.%s" $faviconName .ext | relURL }}{{ $assetBusting }}" rel="icon" {{ .type | safeHTMLAttr }}>
        {{- end }}
        {{- if (fileExists (printf "/static/images/%s-light.%s" $faviconName .ext)) }}
          {{- $faviconMatch = true }}
    <link href="{{ printf "images/%s-light.%s" $faviconName .ext | relURL }}{{ $assetBusting }}" rel="icon" {{ .type | safeHTMLAttr }} media="(prefers-color-scheme: light)">
        {{- end }}
        {{- if (fileExists (printf "/static/images/%s-dark.%s" $faviconName .ext)) }}
          {{- $faviconMatch = true }}
    <link href="{{ printf "images/%s-dark.%s" $faviconName .ext | relURL }}{{ $assetBusting }}" rel="icon" {{ .type | safeHTMLAttr }} media="(prefers-color-scheme: dark)">
        {{- end }}
      {{- end }}
      {{- if $faviconMatch }}
        {{- break }}
      {{- end }}
    {{- end }}