It seems not much people talk about Gant.
Some people compared Maven and Gradle, and if Maven already fulfill the requirement, it may not worth to switch to Gradle.
Does the statement also applies to Gant?
A project I am doing is using Gant, how hard to migrate it to Gradle?
How strong of Groovy skill needed to use Gradle?
Gant is just a lightweight facade on Groovy's AntBuilder. It just a way of scripting Ant tasks using Groovy. Gant can be used to do build tasks, but it doesn't have the integrated artefact dependency management, project lifecycle management, and multi-module/sub-project support that a fully fledged build framework should provide. Gradle on the other hand is a complete build framework based on Groovy and Ivy. If you just want to do some Ant task scripting then Gant is probably the tool you need, but for replacing Ant and Maven as build frameworks (so as to get rid of all the XML and use Groovy), then you probably need to consider Gradle.
And yes, Gant is managed by a Gradle build.
It is probably worth noting that Gradle grew out of work done on Gant.
I think migrating is not that hard. Gant uses AntBuilder and so can Gradle.
Gradle has a build DSL, which you need to know to write the build scripts, but you don't need real Groovy skills for that. Of course it can help if you know Groovy, but you can also get a long way by writing Java code in Gradle build scripts.