feat: Make it possible to access the current commits buffer during co…

…mmit ancestor iteration. (#470)

This is useful to avoid additional lookups of the same object for
reading additional data from it.

Currently one needs an object cache to avoid duplciate object extraction
work, with such a cache being slower than accessing the same buffer
again.

git-traverse/src/commit.rs

@@ -46,6 +46,7 @@ impl Default for Sorting {
 
 ///
 pub mod ancestors {
+    use std::borrow::Borrow;
     use std::{borrow::BorrowMut, collections::VecDeque, iter::FromIterator};
 
     use git_hash::{oid, ObjectId};
@@ -85,6 +86,7 @@ pub mod ancestors {
         }
     }
 
+    /// Builder
     impl<Find, Predicate, StateMut> Ancestors<Find, Predicate, StateMut> {
         /// Change our commit parent handling mode to the given one.
         pub fn parents(mut self, mode: Parents) -> Self {
@@ -93,6 +95,7 @@ pub mod ancestors {
         }
     }
 
+    /// Builder
     impl<Find, Predicate, StateMut, E> Ancestors<Find, Predicate, StateMut>
     where
         Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Result<CommitRefIter<'a>, E>,
@@ -119,6 +122,7 @@ pub mod ancestors {
         }
     }
 
+    /// Initialization
     impl<Find, StateMut, E> Ancestors<Find, fn(&oid) -> bool, StateMut>
     where
         Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Result<CommitRefIter<'a>, E>,
@@ -140,6 +144,7 @@ pub mod ancestors {
         }
     }
 
+    /// Initialization
     impl<Find, Predicate, StateMut, E> Ancestors<Find, Predicate, StateMut>
     where
         Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Result<CommitRefIter<'a>, E>,
@@ -186,6 +191,16 @@ pub mod ancestors {
             }
         }
     }
+    /// Access
+    impl<Find, Predicate, StateMut> Ancestors<Find, Predicate, StateMut>
+    where
+        StateMut: Borrow<State>,
+    {
+        /// Return an iterator for accessing more of the current commits data.
+        pub fn commit_iter(&self) -> CommitRefIter<'_> {
+            CommitRefIter::from_bytes(&self.state.borrow().buf)
+        }
+    }
 
     impl<Find, Predicate, StateMut, E> Iterator for Ancestors<Find, Predicate, StateMut>
     where
@@ -208,6 +223,7 @@ pub mod ancestors {
         }
     }
 
+    /// Utilities
     impl<Find, Predicate, StateMut, E> Ancestors<Find, Predicate, StateMut>
     where
         Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Result<CommitRefIter<'a>, E>,
@@ -272,6 +288,7 @@ pub mod ancestors {
         }
     }
 
+    /// Utilities
     impl<Find, Predicate, StateMut, E> Ancestors<Find, Predicate, StateMut>
     where
         Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Result<CommitRefIter<'a>, E>,