handle won't try to reuse empty buffers to allow it to be claimed (#293)

When detaching an object, it's feasible to avoid cloning as it might
be the last buffer the user needs.

Now that's possble by not reclaiming the empty vec these users would
leave in the original buffers place when the object is dropped.

Author: Byron

git-repository/examples/stats.rs

@@ -4,7 +4,7 @@ use git_odb::FindExt;
 use git_repository as git;
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let repo = git_repository::discover(".")?;
+    let repo = git::discover(".")?;
     println!(
         "Repo: {}",
         repo.work_tree.as_deref().unwrap_or(repo.git_dir()).display()

git-repository/src/easy/handle.rs

@@ -76,6 +76,8 @@ impl easy::Handle {
 
     #[inline]
     pub(crate) fn reuse_buffer(&self, data: &mut Vec<u8>) {
-        self.bufs.borrow_mut().push(std::mem::take(data));
+        if data.capacity() > 0 {
+            self.bufs.borrow_mut().push(std::mem::take(data));
+        }
     }
 }

git-repository/src/easy/object/mod.rs

@@ -81,11 +81,11 @@ impl<'repo> Object<'repo> {
     }
 
     /// Turn this instance into an owned one, copying our data in the process.
-    pub fn into_owned(self) -> DetachedObject {
+    pub fn into_owned(mut self) -> DetachedObject {
         DetachedObject {
             id: self.id,
             kind: self.kind,
-            data: self.data.clone(),
+            data: std::mem::take(&mut self.data),
         }
     }