1 files changed, 112 insertions, 0 deletions
diff --git a/vendor/gix-diff/src/tree/visit.rs b/vendor/gix-diff/src/tree/visit.rs
new file mode 100644
index 000000000..e94c432ae
--- /dev/null
+++ b/vendor/gix-diff/src/tree/visit.rs
@@ -0,0 +1,112 @@
+use gix_hash::ObjectId;
+use gix_object::{bstr::BStr, tree, tree::EntryMode};
+
+/// Represents any possible change in order to turn one tree into another.
+#[derive(Debug, Clone, PartialOrd, PartialEq, Ord, Eq, Hash)]
+pub enum Change {
+    /// An entry was added, like the addition of a file or directory.
+    Addition {
+        /// The mode of the added entry.
+        entry_mode: tree::EntryMode,
+        /// The object id of the added entry.
+        oid: ObjectId,
+    },
+    /// An entry was deleted, like the deletion of a file or directory.
+    Deletion {
+        /// The mode of the deleted entry.
+        entry_mode: tree::EntryMode,
+        /// The object id of the deleted entry.
+        oid: ObjectId,
+    },
+    /// An entry was modified, e.g. changing the contents of a file adjusts its object id and turning
+    /// a file into a symbolic link adjusts its mode.
+    Modification {
+        /// The mode of the entry before the modification.
+        previous_entry_mode: tree::EntryMode,
+        /// The object id of the entry before the modification.
+        previous_oid: ObjectId,
+
+        /// The mode of the entry after the modification.
+        entry_mode: tree::EntryMode,
+        /// The object id after the modification.
+        oid: ObjectId,
+    },
+}
+
+impl Change {
+    /// Return the current object id.
+    pub fn oid(&self) -> &gix_hash::oid {
+        match self {
+            Change::Addition { oid, .. } | Change::Deletion { oid, .. } | Change::Modification { oid, .. } => oid,
+        }
+    }
+    /// Return the current tree entry mode.
+    pub fn entry_mode(&self) -> EntryMode {
+        match self {
+            Change::Addition { entry_mode, .. }
+            | Change::Deletion { entry_mode, .. }
+            | Change::Modification { entry_mode, .. } => *entry_mode,
+        }
+    }
+    /// Return the current object id and tree entry mode of a change.
+    pub fn oid_and_entry_mode(&self) -> (&gix_hash::oid, EntryMode) {
+        match self {
+            Change::Addition { oid, entry_mode }
+            | Change::Deletion { oid, entry_mode }
+            | Change::Modification { oid, entry_mode, .. } => (oid, *entry_mode),
+        }
+    }
+}
+
+/// What to do after a [Change] was [recorded][Visit::visit()].
+#[derive(Clone, Copy, PartialOrd, PartialEq, Ord, Eq, Hash)]
+pub enum Action {
+    /// Continue the traversal of changes.
+    Continue,
+    /// Stop the traversal of changes, making this the last call to [visit(…)][Visit::visit()].
+    Cancel,
+}
+
+impl Default for Action {
+    fn default() -> Self {
+        Action::Continue
+    }
+}
+
+impl Action {
+    /// Returns true if this action means to stop the traversal.
+    pub fn cancelled(&self) -> bool {
+        matches!(self, Action::Cancel)
+    }
+}
+
+/// A trait to allow responding to a traversal designed to figure out the [changes][Change]
+/// to turn tree A into tree B.
+pub trait Visit {
+    /// Sets the full path path in front of the queue so future calls to push and pop components affect it instead.
+    fn pop_front_tracked_path_and_set_current(&mut self);
+    /// Append a `component` to the end of a path, which may be empty.
+    fn push_back_tracked_path_component(&mut self, component: &BStr);
+    /// Append a `component` to the end of a path, which may be empty.
+    fn push_path_component(&mut self, component: &BStr);
+    /// Removes the last component from the path, which may leave it empty.
+    fn pop_path_component(&mut self);
+    /// Record a `change` and return an instruction whether to continue or not.
+    ///
+    /// The implementation may use the current path to lean where in the tree the change is located.
+    fn visit(&mut self, change: Change) -> Action;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn size_of_change() {
+        let actual = std::mem::size_of::<Change>();
+        assert!(
+            actual <= 46,
+            "{actual} <= 46: this type shouldn't grow without us knowing"
+        )
+    }
+}