Add support for routines; state messages

app/classes/state/git/CheckoutState.js

@@ -33,6 +33,13 @@ class CheckoutState extends AbstractGitState {
         }
     }
 
+    failure_message() {
+        return `The Git repo at "${this._config.path}" on host "${this._host.name}" is not checked out to the correct ref (${this._config.target}).`
+    }
+
+    check_message() {
+        return this.failure_message()
+    }
 }
 
 module.exports = exports = CheckoutState

app/classes/state/git/CloneState.js

@@ -21,6 +21,13 @@ class CloneState extends AbstractGitState {
         }
     }
 
+    failure_message() {
+        return `Could not find the cloned Git repo at "${this._config.path}" on host "${this._host.name}."`
+    }
+
+    check_message() {
+        return this.failure_message()
+    }
 }
 
 module.exports = exports = CloneState

app/classes/state/git/TagState.js

@@ -26,6 +26,13 @@ class TagState extends AbstractGitState {
         }
     }
 
+    failure_message() {
+        return `The tag "${this._config.tag}" does not exist in the Git repo "${this._config.path}" on host "${this._host.name}."`
+    }
+
+    check_message() {
+        return this.failure_message()
+    }
 }
 
 module.exports = exports = TagState