Multi-line diffs still show original strings

[mgeisler]

Hello!

I find the multi-line diffs super useful and a main reason to depend on the crate. However, I think they could be made better if they would

• hide the original strings, at least if the strings are very long
• not diff the escaped debug output

Today, I see output like this from AOSP:

---- cargo::metadata::tests::parse_metadata stdout ----
thread 'cargo::metadata::tests::parse_metadata' panicked at development/tools/cargo_embargo/src/cargo/metadata.rs:495:13:

Value of: format!("{crates:#?}")
Expected: is equal to "[\n    [\n        Crate {\n            name: \"either\",\n            package_name: \"either\",\n            version: Some(\n                \"1.9.0\",\n            ),\n            types: [\n                Lib,\n            ],\n            target: Some(\n                \"x86_64-unknown-linux-gnu\",\n            ),\n            features: [\n                \"default\",\n                \"use_std\",\n            ],\n            cfgs: [],\n            externs: [],\n            codegens: [],\n            cap_lints: \"\",\n            static_libs: [],\n            shared_libs: [],\n            edition: \"2018\",\n            package_dir: \".../external/rust/crates/either\",\n            main_src: \"src/lib.rs\",\n            empty_test: false,\n        },\n        Crate {\n            name: \"either\",\n            package_name: \"either\",\n            version: Some(\n                \"1.9.0\",\n            ),\n            types: [\n                Test,\n            ],\n            target: Some(\n                \"x86_64-unknown-linux-gnu\",\n            ),\n            features: [\n                \"default\",\n                \"use_std\",\n            ],\n            cfgs: [],\n            externs: [\n                Extern {\n                    name: \"serde_json\",\n                    lib_name: \"serde_json\",\n                    extern_type: Rust,\n                },\n            ],\n            codegens: [],\n            cap_lints: \"\",\n            static_libs: [],\n            shared_libs: [],\n            edition: \"2018\",\n            package_dir: \".../external/rust/crates/either\",\n            main_src: \"src/lib.rs\",\n            empty_test: false,\n        },\n    ],\n]"
Actual: "[\n    [\n        Crate {\n            name: \"either\",\n            package_name: \"either!\",\n            version: Some(\n                \"1.9.0\",\n            ),\n            types: [\n                Lib,\n            ],\n            target: Some(\n                \"x86_64-unknown-linux-gnu\",\n            ),\n            features: [\n                \"default\",\n                \"use_std\",\n            ],\n            cfgs: [],\n            externs: [],\n            codegens: [],\n            cap_lints: \"\",\n            static_libs: [],\n            shared_libs: [],\n            edition: \"2018\",\n            package_dir: \".../external/rust/crates/either\",\n            main_src: \"src/lib.rs\",\n            empty_test: false,\n        },\n        Crate {\n            name: \"either\",\n            package_name: \"either!\",\n            version: Some(\n                \"1.9.0\",\n            ),\n            types: [\n                Test,\n            ],\n            target: Some(\n                \"x86_64-unknown-linux-gnu\",\n            ),\n            features: [\n                \"default\",\n                \"use_std\",\n            ],\n            cfgs: [],\n            externs: [\n                Extern {\n                    name: \"serde_json\",\n                    lib_name: \"serde_json\",\n                    extern_type: Rust,\n                },\n            ],\n            codegens: [],\n            cap_lints: \"\",\n            static_libs: [],\n            shared_libs: [],\n            edition: \"2018\",\n            package_dir: \".../external/rust/crates/either\",\n            main_src: \"src/lib.rs\",\n            empty_test: false,\n        },\n    ],\n]",
  which isn't equal to "[\n    [\n        Crate {\n            name: \"either\",\n            package_name: \"either\",\n            version: Some(\n                \"1.9.0\",\n            ),\n            types: [\n                Lib,\n            ],\n            target: Some(\n                \"x86_64-unknown-linux-gnu\",\n            ),\n            features: [\n                \"default\",\n                \"use_std\",\n            ],\n            cfgs: [],\n            externs: [],\n            codegens: [],\n            cap_lints: \"\",\n            static_libs: [],\n            shared_libs: [],\n            edition: \"2018\",\n            package_dir: \".../external/rust/crates/either\",\n            main_src: \"src/lib.rs\",\n            empty_test: false,\n        },\n        Crate {\n            name: \"either\",\n            package_name: \"either\",\n            version: Some(\n                \"1.9.0\",\n            ),\n            types: [\n                Test,\n            ],\n            target: Some(\n                \"x86_64-unknown-linux-gnu\",\n            ),\n            features: [\n                \"default\",\n                \"use_std\",\n            ],\n            cfgs: [],\n            externs: [\n                Extern {\n                    name: \"serde_json\",\n                    lib_name: \"serde_json\",\n                    extern_type: Rust,\n                },\n            ],\n            codegens: [],\n            cap_lints: \"\",\n            static_libs: [],\n            shared_libs: [],\n            edition: \"2018\",\n            package_dir: \".../external/rust/crates/either\",\n            main_src: \"src/lib.rs\",\n            empty_test: false,\n        },\n    ],\n]"
  Difference(-actual / +expected):
   [
       [
           Crate {
               name: \"either\",
  -            package_name: \"either!\",
  +            package_name: \"either\",
               version: Some(
                   \"1.9.0\",
   <---- 22 common lines omitted ---->
           Crate {
               name: \"either\",
  -            package_name: \"either!\",
  +            package_name: \"either\",
               version: Some(
                   \"1.9.0\",
   <---- 28 common lines omitted ---->
       ],
   ]
  at development/tools/cargo_embargo/src/cargo/metadata.rs:495:13

The \" in the diff output makes me think that there is some double-escaping going on.