feat: CommitRefIter::parent_ids() (#364)

Allocation-free parent retrieval.

Author: Byron

git-object/src/commit/ref_iter.rs

@@ -17,6 +17,7 @@ pub(crate) enum SignatureKind {
     Committer,
 }
 
+#[derive(Copy, Clone)]
 pub(crate) enum State {
     Tree,
     Parents,
@@ -52,12 +53,22 @@ impl<'a> CommitRefIter<'a> {
         self.next().and_then(Result::ok).and_then(Token::try_into_id)
     }
 
+    /// Return all parent_ids as iterator.
+    ///
+    /// Parsing errors are ignored quietly.
+    pub fn parent_ids(self) -> impl Iterator<Item = git_hash::ObjectId> + 'a {
+        self.filter_map(|t| match t {
+            Ok(Token::Parent { id }) => Some(id),
+            _ => None,
+        })
+    }
+
     /// Returns all signatures, first the author, then the committer, if there is no decoding error.
     ///
     /// Errors are coerced into options, hiding whether there was an error or not. The caller knows if there was an error or not
     /// if not exactly two signatures were iterable.
     /// Errors are not the common case - if an error needs to be detectable, use this instance as iterator.
-    pub fn signatures(&'a mut self) -> impl Iterator<Item = git_actor::SignatureRef<'_>> + 'a {
+    pub fn signatures(self) -> impl Iterator<Item = git_actor::SignatureRef<'a>> + 'a {
         self.filter_map(|t| match t {
             Ok(Token::Author { signature }) | Ok(Token::Committer { signature }) => Some(signature),
             _ => None,

git-object/src/lib.rs

@@ -93,6 +93,7 @@ pub struct CommitRef<'a> {
 
 /// Like [`CommitRef`][crate::CommitRef], but as `Iterator` to support (up to) entirely allocation free parsing.
 /// It's particularly useful to traverse the commit graph without ever allocating arrays for parents.
+#[derive(Copy, Clone)]
 pub struct CommitRefIter<'a> {
     data: &'a [u8],
     state: commit::ref_iter::State,
@@ -212,10 +213,8 @@ pub struct TreeRef<'a> {
 
 /// A directory snapshot containing files (blobs), directories (trees) and submodules (commits), lazily evaluated.
 #[derive(Default, PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone)]
-#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]
 pub struct TreeRefIter<'a> {
     /// The directories and files contained in this tree.
-    #[cfg_attr(feature = "serde1", serde(borrow))]
     data: &'a [u8],
 }
 

git-object/tests/immutable/commit/iter.rs

@@ -112,6 +112,12 @@ fn signed_singleline() -> crate::Result {
             Token::Message(b"update tasks\n".as_bstr()),
         ]
     );
+    assert_eq!(
+        CommitRefIter::from_bytes(&fixture_bytes("commit", "signed-singleline.txt"))
+            .parent_ids()
+            .collect::<Vec<_>>(),
+        vec![hex_to_id("09d8d3a12e161a7f6afb522dbe8900a9c09bce06")]
+    );
     Ok(())
 }
 
@@ -151,6 +157,15 @@ fn mergetag() -> crate::Result {
             Token::Message(LONG_MESSAGE.as_bytes().as_bstr()),
         ]
     );
+    assert_eq!(
+        CommitRefIter::from_bytes(&fixture_bytes("commit", "mergetag.txt"))
+            .parent_ids()
+            .collect::<Vec<_>>(),
+        vec![
+            hex_to_id("44ebe016df3aad96e3be8f95ec52397728dd7701"),
+            hex_to_id("8d485da0ddee79d0e6713405694253d401e41b93")
+        ]
+    );
     Ok(())
 }
 
@@ -174,6 +189,12 @@ mod method {
                 .collect::<Vec<_>>(),
             vec![signature(1592437401), signature(1592437401)]
         );
+        assert_eq!(
+            CommitRefIter::from_bytes(&fixture_bytes("commit", "unsigned.txt"))
+                .parent_ids()
+                .count(),
+            0
+        );
         Ok(())
     }