Local tasks for node not visible on diff.revisions_diff route

Added also tests to make sure the local tabs are visible.

Patch #5 worked for my Drupal 9.5.11 site.
I added the following to the composer.json file
"patches": {
"drupal/diff": {
Displays local tasks on revisions sub-tab: " https://www.drupal.org/files/issues/2023-10-05/2954352-diff-show-local-t... → "
}
}

+1 for RTBC

Great and simple improvement. Thanks!

Unfortunately this has caused issues on Node revision pages when there is more than one secondary tab (which is what is required to actually render the link)

Symfony\Component\Routing\Exception\MissingMandatoryParametersException: Some mandatory parameters are missing ("left_revision", "right_revision", "filter") to generate a URL for route "diff.revisions_diff". in Drupal\Core\Routing\UrlGenerator->doGenerate() (line 187 of core/lib/Drupal/Core/Routing/UrlGenerator.php). 

@acbramley could you provide a bit more information about the issue you have faced? I'm not being able to reproduce it on route diff.revisions_diff eg. /node/1/revisions, when selecting also "Show primary tabs" on "Secondary tabs" blocks.

@sokru you need to have at least 1 other secondary tab to trigger it.

This patch is a port of the patch in #3169729: No local tasks on compare revisions page → . It should avoid the problem mentioned in #12.

Please use a merge request, patch files are not accepted on this project anymore.