fix: keep a path's bytes, so a filename that is not utf-8 survives

src/cmd/docker.rs

@@ -1,3 +1,6 @@
+use std::ffi::OsString;
+use std::path::Path;
+
 use super::{Argv, Cmd};
 
 // docker exec, around a command that runs inside the container
@@ -47,24 +50,25 @@ impl Cmd for Exec {
     }
 }
 
-// docker cp, in either direction
+// docker cp, in either direction. the local side stays an OsString: it is a
+// path the user named, and a lossy one would copy something else
 pub struct Cp {
-    from: String,
-    to: String,
+    from: OsString,
+    to: OsString,
 }
 
 impl Cp {
-    pub fn into_container(local: &str, container: &str, remote: &str) -> Self {
+    pub fn into_container(local: &Path, container: &str, remote: &str) -> Self {
         Self {
-            from: local.to_string(),
-            to: format!("{container}:{remote}"),
+            from: local.as_os_str().to_owned(),
+            to: OsString::from(format!("{container}:{remote}")),
         }
     }
 
-    pub fn out_of_container(container: &str, remote: &str, local: &str) -> Self {
+    pub fn out_of_container(container: &str, remote: &str, local: &Path) -> Self {
         Self {
-            from: format!("{container}:{remote}"),
-            to: local.to_string(),
+            from: OsString::from(format!("{container}:{remote}")),
+            to: local.as_os_str().to_owned(),
         }
     }
 }