Change: keep actual text of keyword from scenario

The typesetting should preserve the actual keyword or alias in the
source. Previously, if source had this:

```
given foo
and bar
```

it got typeset as if were:

```
given foo
given bar
```

Also, change subplot.md to use alias when possible.

1 files changed, 22 insertions, 10 deletions

diff --git a/src/steps.rs b/src/steps.rs
index 2c6f34f..1cbdfe5 100644
--- a/src/steps.rs
+++ b/src/steps.rs
@@ -14,14 +14,16 @@ use std::fmt;
 #[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
 pub struct ScenarioStep {
     kind: StepKind,
+    keyword: String,
     text: String,
 }
 
 impl ScenarioStep {
     /// Construct a new step.
-    pub fn new(kind: StepKind, text: &str) -> ScenarioStep {
+    pub fn new(kind: StepKind, keyword: &str, text: &str) -> ScenarioStep {
         ScenarioStep {
             kind,
+            keyword: keyword.to_owned(),
             text: text.to_owned(),
         }
     }
@@ -31,6 +33,11 @@ impl ScenarioStep {
         self.kind
     }
 
+    /// Return the actual textual keyword of a step.
+    pub fn keyword(&self) -> &str {
+        &self.keyword
+    }
+
     /// Return the text of a step.
     pub fn text(&self) -> &str {
         &self.text
@@ -43,13 +50,18 @@ impl ScenarioStep {
     pub fn new_from_str(text: &str, default: Option<StepKind>) -> Result<ScenarioStep> {
         let mut words = text.split_whitespace();
 
-        let kind = match words.next() {
-            Some("given") => StepKind::Given,
-            Some("when") => StepKind::When,
-            Some("then") => StepKind::Then,
-            Some("and") => default.ok_or(SubplotError::ContinuationTooEarly)?,
-            Some("but") => default.ok_or(SubplotError::ContinuationTooEarly)?,
-            _ => return Err(SubplotError::UnknownStepKind),
+        let keyword = match words.next() {
+            Some(s) => s,
+            _ => return Err(SubplotError::NoStepKeyword(text.to_string())),
+        };
+
+        let kind = match keyword {
+            "given" => StepKind::Given,
+            "when" => StepKind::When,
+            "then" => StepKind::Then,
+            "and" => default.ok_or(SubplotError::ContinuationTooEarly)?,
+            "but" => default.ok_or(SubplotError::ContinuationTooEarly)?,
+            _ => return Err(SubplotError::UnknownStepKind(keyword.to_string())),
         };
 
         let mut joined = String::new();
@@ -60,13 +72,13 @@ impl ScenarioStep {
         if joined.len() > 1 {
             joined.pop();
         }
-        Ok(ScenarioStep::new(kind, &joined))
+        Ok(ScenarioStep::new(kind, keyword, &joined))
     }
 }
 
 impl fmt::Display for ScenarioStep {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{} {}", self.kind(), self.text())
+        write!(f, "{} {}", self.keyword(), self.text())
     }
 }