add-categories.txt

If category information is missing in content.jar [1], proceed as following:

$ jar xf content.jar content.xml

Add to content.xml:

    <unit id='Enhanced Class Decompiler (Core)' version='1.0.0.47I-cJWjHh7735G3I5C'>
      <properties size='3'>
        <property name='org.eclipse.equinox.p2.name' value='Enhanced Class Decompiler (Core)'/>
        <property name='org.eclipse.equinox.p2.description' value='Enhanced Class Decompiler integrates JD, Jad, FernFlower, CFR, Procyon with Eclipse seamlessly. It allows Java developers to debug class files without source code directly.'/>
        <property name='org.eclipse.equinox.p2.type.category' value='true'/>
      </properties>
      <provides size='1'>
        <provided namespace='org.eclipse.equinox.p2.iu' name='Enhanced Class Decompiler (Core)' version='1.0.0.47I-cJWjHh7735G3I5C'/>
      </provides>
      <requires size='1'>
        <required namespace='org.eclipse.equinox.p2.iu' name='org.sf.feeling.decompiler.feature.group' range='[3.0.0.201709070937,3.0.0.201709070937]'/>
      </requires>
      <touchpoint id='null' version='0.0.0'/>
    </unit>    
    <unit id='Enhanced Class Decompiler (Optional)' version='1.0.0.7J8Y-cJWhMb7cITNJXT4'>
      <properties size='3'>
        <property name='org.eclipse.equinox.p2.name' value='Enhanced Class Decompiler (Optional)'/>
        <property name='org.eclipse.equinox.p2.description' value='Enhanced Class Decompiler integrates JD, Jad, FernFlower, CFR, Procyon with Eclipse seamlessly. It allows Java developers to debug class files without source code directly.'/>
        <property name='org.eclipse.equinox.p2.type.category' value='true'/>
      </properties>
      <provides size='1'>
        <provided namespace='org.eclipse.equinox.p2.iu' name='Enhanced Class Decompiler (Optional)' version='1.0.0.7J8Y-cJWhMb7cITNJXT4'/>
      </provides>
      <requires size='5'>
        <required namespace='org.eclipse.equinox.p2.iu' name='org.sf.feeling.decompiler.jad.feature.group' range='[3.0.0.201709070937,3.0.0.201709070937]'>
          <filter>
            (&amp;(|(osgi.arch=x86)(osgi.arch=x86_64))(|(osgi.os=linux)(osgi.os=macosx)(osgi.os=win32)))
          </filter>
        </required>
        <required namespace='org.eclipse.equinox.p2.iu' name='org.sf.feeling.decompiler.cfr.feature.group' range='[3.0.0.201709070937,3.0.0.201709070937]'/>
        <required namespace='org.eclipse.equinox.p2.iu' name='org.sf.feeling.decompiler.source.feature.group' range='[3.0.0.201709070937,3.0.0.201709070937]'/>
        <required namespace='org.eclipse.equinox.p2.iu' name='org.sf.feeling.decompiler.procyon.feature.group' range='[3.0.0.201709070937,3.0.0.201709070937]'/>
        <required namespace='org.eclipse.equinox.p2.iu' name='org.sf.feeling.decompiler.jd.feature.group' range='[3.0.0.201709070937,3.0.0.201709070937]'>
          <filter>
            (&amp;(|(osgi.arch=x86)(osgi.arch=x86_64))(|(osgi.os=linux)(osgi.os=macosx)(osgi.os=win32)))
          </filter>
        </required>
      </requires>
      <touchpoint id='null' version='0.0.0'/>
    </unit>
    
update version numbers and increase size param of <units> by 2
 
$ jar uf content.jar content.xml

[1] https://bugs.eclipse.org/bugs/show_bug.cgi?id=278673