Add basic tests for lockfile generation (#3623)

crates/uv/src/cli.rs

@@ -1337,7 +1337,7 @@ pub(crate) struct PipInstallArgs {
     #[arg(long)]
     pub(crate) dry_run: bool,
 
-    #[arg(long, hide = true)]
+    #[arg(long, hide = true, group = "sources")]
     pub(crate) unstable_uv_lock_file: Option<String>,
 
     #[command(flatten)]

crates/uv/src/commands/pip/install.rs

@@ -179,7 +179,12 @@ pub(crate) async fn pip_install(
     // If the requirements are already satisfied, we're done. Ideally, the resolver would be fast
     // enough to let us remove this check. But right now, for large environments, it's an order of
     // magnitude faster to validate the environment than to resolve the requirements.
-    if reinstall.is_none() && upgrade.is_none() && source_trees.is_empty() && overrides.is_empty() {
+    if reinstall.is_none()
+        && upgrade.is_none()
+        && source_trees.is_empty()
+        && overrides.is_empty()
+        && uv_lock.is_none()
+    {
         match site_packages.satisfies(&requirements, &editables, &constraints)? {
             SatisfiesResult::Fresh {
                 recursive_requirements,