Fix record signatures based on data provided by mappings. (#507)

Reads "extras/record_signatures.json" from mappings jar, just works with yarn.

Mojmap:

```
mappings loom.layered {
   officialMojangMappings()
   signatureFix("net.fabricmc:yarn:21w38a+build.9:v2")
}
```

1 files changed, 6 insertions, 0 deletions

diff --git a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
index 05180172..fd16f23c 100644
--- a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
@@ -47,4 +47,10 @@ public interface LayeredMappingSpecBuilder {
 	}
 
 	LayeredMappingSpecBuilder parchment(Object object, Action<ParchmentMappingsSpecBuilder> action);
+
+	/**
+	 * Add a signatureFix layer. Reads the @extras/record_signatures.json" file in a jar file such as yarn.
+	 */
+	@ApiStatus.Experimental
+	LayeredMappingSpecBuilder signatureFix(Object object);
 }