fix: allow final word to be wrapped in wrap_help

Before, inserting a newline did not move the prev_space index forward.
This meant that the next word was measured incorrectly since the
length was measured back to the word before the newly inserted
linebreak.

Fixes clap-rs#828.

src/app/help.rs

@@ -960,8 +960,21 @@ fn wrap_help(help: &mut String, longest_w: usize, avail_chars: usize) {
             debugln!("Help::wrap_help:iter: Char at {}: {:?}", j, &help[j..j+1]);
             help.remove(j);
             help.insert(j, '\n');
+            prev_space = idx;
         }
     } else {
         sdebugln!("No");
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn wrap_help_last_word() {
+        let mut help = String::from("foo bar baz");
+        wrap_help(&mut help, 3, 5);
+        assert_eq!(help, "foo\nbar\nbaz");
+    }
+}

tests/help.rs

@@ -159,7 +159,8 @@ FLAGS:
             information
     -V, --version
             Prints
-            version information";
+            version
+            information";
 
 static OLD_NEWLINE_CHARS: &'static str = "ctest 0.1