Shifter now supports appending URLs on your site.

How to apply

Insert following filter to functions.php on your theme.

Code

add_filter( 'ShifterURLS::AppendURLtoAll', 'my_append_urls' );

Limitations

URLs should be contained in WordPress (Shifter can't fetch external URLs)
URLs should be embedded in home_url("")
URLs should end with a slash (tailing slash) or allowed a listed suffix.
URLs will be generated with /index.html.
Content-Type will be same as what Shifter fetched from WordPress
(e.g. /wp-json/wp/v2/posts/ will be /wp-json/wp/v2/posts/index.html and delivered as content-type: application/json.)

Allowed file suffixes

.html
.xml
.rss
.rdf
.atom
.css
.js
.json

Samples

Sample Code A

Adding /wp-json/wp/v2/posts/ to the target URLs of the generator

function my_append_urls( $urls ) {
    $urls[] = home_url('/wp-json/wp/v2/posts/');
    return $urls;
}
add_action( 'init', function(){
    add_filter( 'ShifterURLS::AppendURLtoAll', 'my_append_urls' );
} );

Results A

/wp-json/wp/v2/posts/ ịs added to the target URL as "link_type": "from_filter_hook" and "path": "/wp-json/wp/v2/posts/".

$ curl -s https://127.0.0.1:8443/?urls | jq .

{
  "datetime": "2020-07-07 02:41:39 UTC",
  "page": null,
  "start": 0,
  "end": 100,
  "limit": 100,
  "items": [
    {
      "link_type": "home",
      "post_type": "",
      "link": "https://127.0.0.1:8443/",
      "path": "/"
    },

[... cropped ...]

    {
      "link_type": "from_filter_hook",
      "post_type": "",
      "link": "https://127.0.0.1:8443/wp-json/wp/v2/posts/",
      "path": "/wp-json/wp/v2/posts/"
    }
  ],
  "request_type": "TOP",
  "request_path": "/",
  "count": 20,
  "finished": true
}

Sample Code B

Appending the list of the stats of US as /states/($slag)/ to the target URL.

function my_append_urls( $urls ) {
$states = [
'Alabama',
'Arizona',

[...cropped....]

'Wisconsin',
'Wyoming',
	];
foreach ( $states as $slag ) {
$urls[] = home_url("/states/{$slag}/");
}
return $urls;
}
add_action( 'init', function(){
add_filter( 'ShifterURLS::AppendURLtoAll', 'my_append_urls' );
} );

Sample Result B

$ curl -s https://127.0.0.1:8443/wp-json/shifter/v1/urls?page=1 | jq .
{
  "datetime": "2020-09-04 06:01:58 UTC",
  "page": 1,
  "start": 100,
  "end": 200,
  "limit": 100,
  "items": [
    {
      "link_type": "term_feed",
      "post_type": "column",
      "link": "https://127.0.0.1:8443/column/feed/",
      "path": "/column/feed/"
    },
  :
    {
      "link_type": "from_filter_hook",
      "post_type": "",
      "link": "https://127.0.0.1:8443/states/Alabama/",
      "path": "/states/Alabama/"
    },
    {
      "link_type": "from_filter_hook",
      "post_type": "",
      "link": "https://127.0.0.1:8443/states/Arizona/",
      "path": "/states/Arizona/"
    },

[..... cropped .......]

    {
      "link_type": "from_filter_hook",
      "post_type": "",
      "link": "https://127.0.0.1:8443/states/Wisconsin/",
      "path": "/states/Wisconsin/"
    },
    {
      "link_type": "from_filter_hook",
      "post_type": "",
      "link": "https://127.0.0.1:8443/states/Wyoming/",
      "path": "/states/Wyoming/"
    }
  ],
  "request_type": "TOP",
  "request_path": "/",
  "count": 91,
  "finished": true
}