Make it easier to grasp the before and after states of the create_wd_tree() tests.

Also optimize the tests for reading by removing the .unwrap() calls and
reducing the verbosity of variable names.

Author: Byron

Cargo.lock

@@ -39,3 +39,4 @@ path = "tests/mod.rs"
 gitbutler-testsupport.workspace = true
 gitbutler-user.workspace = true
 serde_json = { version = "1.0", features = ["std", "arbitrary_precision"] }
+insta = "1.41.1"