add api to merge params

Author: Simon-Laux

src/param.rs

@@ -440,6 +440,15 @@ impl Params {
         self.set(key, format!("{value}"));
         self
     }
+
+    /// Merge in parameters from other Params struct,
+    /// overwriting the keys that are in both
+    /// with the values from the new Params struct.
+    pub fn merge_in_from_params(&mut self, new_params: Self) -> &mut Self {
+        let mut new_params = new_params;
+        self.inner.append(&mut new_params.inner);
+        self
+    }
 }
 
 #[cfg(test)]
@@ -502,4 +511,18 @@ mod tests {
         assert_eq!(p.get(Param::Height), Some("14"));
         Ok(())
     }
+
+    #[test]
+    fn test_merge() -> Result<()> {
+        let mut p = Params::from_str("w=12\na=5\nh=14")?;
+        let p2 = Params::from_str("L=1\nh=17")?;
+        assert_eq!(p.len(), 3);
+        p.merge_in_from_params(p2);
+        assert_eq!(p.len(), 4);
+        assert_eq!(p.get(Param::Width), Some("12"));
+        assert_eq!(p.get(Param::Height), Some("17"));
+        assert_eq!(p.get(Param::Forwarded), Some("5"));
+        assert_eq!(p.get(Param::IsEdited), Some("1"));
+        Ok(())
+    }
 }