Most of the refactor. Need to switch machines.

crates/core/src/error.rs

@@ -0,0 +1,25 @@
+use derive_more::{Display, From};
+
+pub type Result<T> = core::result::Result<T, Error>;
+
+#[derive(Debug, From, Display)]
+pub enum Error {
+    #[from]
+    Io(io::Error),
+
+    #[from]
+    Java(java::Error),
+
+    MissingFileName,
+
+    #[from]
+    StdIo(std::io::Error),
+
+    #[from]
+    TomlDeserialize(toml::de::Error),
+
+    #[from]
+    TomlSerialize(toml::ser::Error),
+
+    UnknownPackage,
+}