Redesign terminal support

Replace the closed enum with an open
Terminal trait and dynamic dispatch.

Makes it easier to add new terminals,
and to feature-switch terminals at compile
time for better platform support.

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html
 ### Added
 - `mdcat` builds on Windows now (see [GH-34][]).
 
+### Changed
+- Refactor internal terminal representation, replacing the terminal enum with a
+  new `Terminal` trait and dynamic dispatch.
+
 [GH-34]: https://github.com/lunaryorn/mdcat/pull/34
 
 ## [0.8.0] – 2018-02-15

Cargo.toml

@@ -15,13 +15,23 @@ authors = ["Sebastian Wiesner <sebastian@swsnr.de>"]
 travis-ci = { repository = "lunaryorn/mdcat" }
 maintenance = { status = "actively-developed" }
 
+[features]
+default = ["iterm2", "terminology"]
+
+iterm2 = ["mime", "base64"]
+terminology = ["immeta"]
+
 [dependencies]
 atty = "^0.2"
 failure = "^0.1"
 reqwest = "^0.8"
 term_size = "^0.3"
 url = "^1.6"
 
+mime = {version = "^0.3", optional = true}
+base64 = {version = "^0.9", optional = true}
+immeta = {version = "^0.4", optional = true}
+
 [dependencies.clap]
 version = "^2.29"
 default-features = false
@@ -37,13 +47,6 @@ version = "^2"
 default-features = false
 features = ["parsing", "assets", "dump-load"]
 
-[target.'cfg(target_os = "macos")'.dependencies]
-mime = "^0.3"
-base64 = "^0.9"
-
-[target.'cfg(all(unix, not(target_os = "macos")))'.dependencies]
-immeta = "^0.4"
-
 [package.metadata.release]
 sign-commit = true
 upload-doc = false