Implement object checkout in PrepareCheckout

gix/src/clone/checkout.rs

@@ -5,6 +5,7 @@ use crate::{clone::PrepareCheckout, Repository};
 pub mod main_worktree {
     use std::{path::PathBuf, sync::atomic::AtomicBool};
 
+    use crate::ext::ObjectIdExt;
     use crate::{clone::PrepareCheckout, Progress, Repository};
 
     /// The error returned by [`PrepareCheckout::main_worktree()`].
@@ -60,6 +61,13 @@ pub mod main_worktree {
 
     /// Modification
     impl PrepareCheckout {
+        /// Set the reference to checkout from the tree.
+        pub fn with_rev_single(mut self, object_id: Option<gix_hash::ObjectId>) -> PrepareCheckout {
+            self.checkout_object = object_id;
+
+            self
+        }
+
         /// Checkout the main worktree, determining how many threads to use by looking at `checkout.workers`, defaulting to using
         /// on thread per logical core.
         ///
@@ -97,8 +105,8 @@ pub mod main_worktree {
                 git_dir: repo.git_dir().to_owned(),
             })?;
 
-            let root_tree_id = match &self.ref_name {
-                Some(reference_val) => Some(repo.find_reference(reference_val)?.peel_to_id_in_place()?),
+            let root_tree_id = match self.checkout_object {
+                Some(reference_val) => Some(reference_val.attach(repo)),
                 None => repo.head()?.try_peel_to_id_in_place()?,
             };
 

gix/src/clone/fetch/mod.rs

@@ -37,6 +37,9 @@ pub enum Error {
     },
     #[error("Failed to update HEAD with values from remote")]
     HeadUpdate(#[from] crate::reference::edit::Error),
+    #[cfg(feature = "revision")]
+    #[error("Failed to parse revision")]
+    RefParseError(#[from] crate::revision::spec::parse::single::Error),
     #[error("The remote didn't have any ref that matched '{}'", wanted.as_ref().as_bstr())]
     RefNameMissing { wanted: gix_ref::PartialName },
     #[error("The remote has {} refs for '{}', try to use a specific name: {}", candidates.len(), wanted.as_ref().as_bstr(), candidates.iter().filter_map(|n| n.to_str().ok()).collect::<Vec<_>>().join(", "))]
@@ -229,13 +232,19 @@ impl PrepareFetch {
         P::SubProgress: 'static,
     {
         let (repo, fetch_outcome) = self.fetch_only(progress, should_interrupt)?;
-        Ok((
-            crate::clone::PrepareCheckout {
-                repo: repo.into(),
-                ref_name: self.ref_name.clone(),
-            },
-            fetch_outcome,
-        ))
+
+        let mut checkout = crate::clone::PrepareCheckout {
+            repo: repo.into(),
+            checkout_object: None,
+        };
+
+        if let Some(ref_name) = self.ref_name.as_ref() {
+            let bstring: &gix_ref::PartialNameRef = ref_name.as_ref();
+            let rev = checkout.repo().rev_parse_single(bstring.as_bstr())?.detach();
+            checkout = checkout.with_rev_single(Some(rev));
+        }
+
+        Ok((checkout, fetch_outcome))
     }
 }
 

gix/src/clone/mod.rs

@@ -138,8 +138,8 @@ impl PrepareFetch {
 pub struct PrepareCheckout {
     /// A freshly initialized repository which is owned by us, or `None` if it was successfully checked out.
     pub(self) repo: Option<crate::Repository>,
-    /// The name of the reference to check out. If `None`, the reference pointed to by `HEAD` will be checked out.
-    pub(self) ref_name: Option<gix_ref::PartialName>,
+    /// The object that will be checked out, or `None` if checking out HEAD.
+    pub(self) checkout_object: Option<gix_hash::ObjectId>,
 }
 
 // This module encapsulates functionality that works with both feature toggles. Can be combined with `fetch`