Remove target children with duplicate ID before append/prepend

[jeromecornet]

Fixes #132

@dhh this implements Option C of #132 (comment)

When appending/prepending, children of the template may contain the same ID as children of the existing target.
(this is common when using turbo-rails or other frameworks where the append/prepend action comes both as a result of the response to the original action and as a broadcasted action from a background job).

When this is the case, the generated result contains duplicate children ID which is undesirable.

This PR changes the behaviour of the append/prepend actions so that the existing children of the target which match the children of the template are removed before appending the template.

Assuming the following contrived example:
Target:

<ul id="vehicles">
  <li id="vehicle_1">Old car</li>
  <li id="vehicle_2">New car</li>
</ul>

Stream element:

<turbo-stream action="append" target="vehicles">
  <template>
      <li id="vehicle_1">Old car with updates</li>
      <li id="vehicle_3">Newer car</li>
  </template>
</turbo-stream>

With the current code, the result is:

<ul id="vehicles">
  <li id="vehicle_1">Old car</li>
  <li id="vehicle_2">New car</li>
  <li id="vehicle_1">Old car with updates</li>
  <li id="vehicle_3">Newer car</li>
</ul>

This PR changes it so the result is

<ul id="vehicles">
  <li id="vehicle_2">New car</li>
  <li id="vehicle_1">Old car with updates</li>
  <li id="vehicle_3">Newer car</li>
</ul>

[acushlakoncept]

I am currently having this issue, how do I apply the solution in my code as the PR is yet to be merged?

[jeromecornet]

I am currently having this issue, how do I apply the solution in my code as the PR is yet to be merged?

@acushlakoncept if you are using turbo-rails with sprockets, I have created a temporary fork with a patched turbo.js until this gets merged.
gem "turbo-rails", github: "jeromecornet/turbo-rails", branch: "dedup"

[acushlakoncept]

Thank you @jeromecornet, is gem "turbo-rails" ... different from gem 'hotwire-rails' that I had?
Sorry I am new with turbo stuff

[jeromecornet]

@acushlakoncept The gem hotwire-rails depends on the other gem turbo-rails, so if you only have hotwire-rails in your Gemfile, add another line as mentioned above to force the version of turbo-rails, until both turbo and turbo-rails get updated with that fix.