Syntax highlighting for source code of urdf & sdf (xml-based) files on Github

Question

Note: I posted this on stack overflow but couldn't get an answer. I am trying it here.

I have files that are in urdf [Unified Robot Description Format] for ROS and sdf [Simulation Description Format] for gazebo. URDF is xml but Github only shows it in black. How can I get Github to show syntax highlighting on the file? Can I do this for any file extension including a missing extension?

NOTE: I am not referring to comments in markdown so back ticks don't apply.

<sdf version='1.6'>
  <world name='default'>

    <include>
      <uri>model://ground_plane</uri>
    </include>

    <include>
      <pose frame=''>0 0 30 0 0 0</pose>
      <uri>model://robot</uri>
    </include>

...


  </world>
</sdf>

Stack Overflow's syntax highlighting seems to get it.

Answer 1

The GitHub page on code blocks has a section on syntax highlighting that says:

Syntax highlighting

You can add an optional language identifier to enable syntax highlighting in your fenced code block.

For example, to syntax highlight Ruby code:

```ruby
require 'redcarpet'
markdown = Redcarpet.new("Hello World!")
puts markdown.to_html
```

More information is provided below that example:

We use Linguist to perform language detection and to select third-party grammars for syntax highlighting. You can find out which keywords are valid in the languages YAML file.

In reviewing the third-party grammars it looks like URDF specifically isn't included, but XML is. Since the URDF "is an XML format for representing a robot model," I'd just tag the block as XML.

:EDIT:

Just re-read and you say you're asking about files, not comments, but I checked a URDF file here and it looks like the following for me:

If there's some other issue you've got please link a specific example where it's not working for you.