Add default implementations for formats

This is "self-document" the intent and codify the default value for the
input and output formats.

src/asciicast.rs

@@ -26,7 +26,6 @@ use strum::{EnumString, EnumVariantNames, VariantNames};
 
 pub const VERSION: usize = 2;
 pub const DEFAULT_HEIGHT: &str = "24";
-
 pub const DEFAULT_SHELL: &str = "/bin/sh";
 pub const DEFAULT_TERM: &str = "xterm-256color";
 pub const DEFAULT_WIDTH: &str = "80";

src/main.rs

@@ -24,25 +24,37 @@ use std::path::PathBuf;
 use std::process;
 use structopt::clap::{self, value_t, ArgMatches};
 use structopt::StructOpt;
-use strum::{EnumString, EnumVariantNames, VariantNames};
+use strum::{Display, EnumString, EnumVariantNames, VariantNames};
 
 pub const DEFAULT_INTERACTIVE_PROMPT: &str = ">>> ";
 
-#[derive(Debug, EnumString, EnumVariantNames)]
+#[derive(Display, Debug, EnumString, EnumVariantNames)]
 #[strum(serialize_all = "lowercase")]
 enum InputFormats {
     Germ,
     TermSheets,
 }
 
-#[derive(Debug, EnumString, EnumVariantNames)]
+impl Default for InputFormats {
+    fn default() -> Self {
+        Self::Germ
+    }
+}
+
+#[derive(Display, Debug, EnumString, EnumVariantNames)]
 #[strum(serialize_all = "lowercase")]
 enum OutputFormats {
     Germ,
     TermSheets,
     Asciicast,
 }
 
+impl Default for OutputFormats {
+    fn default() -> Self {
+        Self::Asciicast
+    }
+}
+
 #[derive(Debug, StructOpt)]
 #[structopt(settings(&[
     clap::AppSettings::NoBinaryName,
@@ -121,7 +133,7 @@ struct Cli {
         long,
         possible_values = InputFormats::VARIANTS,
         case_insensitive = true,
-        default_value = "germ",
+        default_value,
         value_name = "format",
         env = "GERM_INPUT_FORMAT"
     )]
@@ -139,7 +151,7 @@ struct Cli {
         long,
         possible_values = OutputFormats::VARIANTS,
         case_insensitive = true,
-        default_value = "asciicast",
+        default_value,
         default_value_if("use-germ-format", None, "germ"),
         value_name = "format",
         env = "GERM_OUTPUT_FORMAT"