expose merge method in python (#1372)

Author: TomNicholas

icechunk-python/python/icechunk/_icechunk_python.pyi

@@ -1360,6 +1360,25 @@ class RepositoryConfig:
         Clear all virtual chunk containers from the repository.
         """
         ...
+    def merge(self, other: RepositoryConfig) -> RepositoryConfig:
+        """
+        Merge another RepositoryConfig with this one.
+
+        When merging, values from the other config take precedence. For nested configs
+        (compression, caching, manifest, storage), the merge is applied recursively.
+        For virtual_chunk_containers, entries from the other config extend this one.
+
+        Parameters
+        ----------
+        other: RepositoryConfig
+            The configuration to merge with this one.
+
+        Returns
+        -------
+        RepositoryConfig
+            A new merged configuration.
+        """
+        ...
 
 class Diff:
     """The result of comparing two snapshots"""

icechunk-python/src/config.rs

@@ -1594,6 +1594,12 @@ impl PyRepositoryConfig {
         Ok(c.get_virtual_chunk_container(name).map(|c| c.clone().into()))
     }
 
+    pub fn merge(&self, other: &PyRepositoryConfig) -> PyResult<PyRepositoryConfig> {
+        let this: RepositoryConfig = self.try_into().map_err(PyValueError::new_err)?;
+        let other: RepositoryConfig = other.try_into().map_err(PyValueError::new_err)?;
+        Ok(this.merge(other).into())
+    }
+
     pub fn __repr__(&self) -> String {
         #[allow(clippy::expect_used)]
         Python::attach(|py| {