Gradle task configuration for mod decompilation. "remapMcSources" is final task here.

build.gradle

deobfMcSRG{
    setFailOnAtError(false)
    setInJar('lib/Thaumcraft-1.12.2-6.1.BETA26.jar')
    setOutJar('lib/TC-1.jar')
}

decompileMc{
    setInJar('lib/TC-1.jar')
    setOutJar('lib/TC-2.jar')
}

fixMcSources{
    setInJar('lib/TC-2.jar')
    setOutJar('lib/TC-3.jar')
}

remapMcSources{
    setInJar('lib/TC-3.jar')
    setOutJar('lib/TC-4.jar')
}