Use non-ephemeral workspace

src/cargo/core/workspace.rs

@@ -198,9 +198,7 @@ impl<'cfg> Workspace<'cfg> {
         target_dir: Option<Filesystem>,
         require_optional_deps: bool,
     ) -> CargoResult<Workspace<'cfg>> {
-        let manifest_path = package.manifest_path();
-        let mut ws = Workspace::new_default(manifest_path.to_path_buf(), config);
-        ws.root_manifest = ws.find_root(&manifest_path)?;
+        let mut ws = Workspace::new_default(package.manifest_path().to_path_buf(), config);
         ws.is_ephemeral = true;
         ws.require_optional_deps = require_optional_deps;
         let key = ws.current_manifest.parent().unwrap();
@@ -831,6 +829,17 @@ impl<'cfg> Workspace<'cfg> {
         }
         Ok(())
     }
+
+    pub fn set_target_dir(&mut self, target_dir: Filesystem) {
+        self.target_dir = Some(target_dir);
+    }
+
+    // TODO: This seems like the wrong approach
+    pub fn set_package(&mut self, package: Package) {
+        let key = self.current_manifest.parent().unwrap();
+        let package = MaybePackage::Package(package);
+        self.packages.packages.insert(key.to_path_buf(), package);
+    }
 }
 
 impl<'cfg> Packages<'cfg> {

src/cargo/ops/cargo_install.rs

@@ -202,7 +202,7 @@ fn install_one(
 
     let mut td_opt = None;
     let mut needs_cleanup = false;
-    let overidden_target_dir = if source_id.is_path() {
+    let overidden_target_dir = if source_id.is_git() || source_id.is_path() {
         None
     } else if let Some(dir) = config.target_dir()? {
         Some(dir)
@@ -220,6 +220,17 @@ fn install_one(
         None => {
             let mut ws = Workspace::new(pkg.manifest_path(), config)?;
             ws.set_require_optional_deps(false);
+
+            // Use tempdir to build git depedencies to prevent bloat in cargo cache
+            if source_id.is_git() && config.target_dir()?.is_none() {
+                match TempFileBuilder::new().prefix("cargo-install").tempdir() {
+                    Ok(td) => ws.set_target_dir(Filesystem::new(td.path().to_owned())),
+                    // If tempfile creation fails, write to cargo cache but clean up afterwards
+                    Err(_) => needs_cleanup = true,
+                }
+            }
+            ws.set_package(pkg);
+
             ws
         }
     };