Method try_merge

atomic-core/src/merge/engine.rs:89–217

Attempt to merge a conflict group using token-level semantics. # Algorithm 1. Extract the two competing vertices (only 2-way supported). 2. Retrieve content bytes for both from the [`ChangeStore`]. 3. Find the common ancestor vertex — the dead vertex that both competing changes deleted. 4. Retrieve content bytes for the ancestor. 5. Tokenize all three byte sequences. 6. Run a three-way diff at t

(&self, group: &ConflictGroup)

    ///
    /// Returns [`PristineError`] on database access failure.
    pub fn try_merge(&self, group: &ConflictGroup) -> Result<MergeOutcome, PristineError> {
        // Only two-way conflicts are candidates (the most common case).
        if group.vertex_count() != 2 {
            log::debug!(
                "SemanticMergeEngine::try_merge: skipping {}-way conflict (only 2-way supported)",
                group.vertex_count(),
            );
            return Ok(MergeOutcome::NoCrdtData);
        }

        let v_left = &group.vertices[0];
        let v_right = &group.vertices[1];

        // Step 1-2: Get content bytes for both competing vertices.
        let left_content = match self.get_vertex_content(v_left) {
            Ok(c) => c,
            Err(e) => {
                log::debug!(
                    "SemanticMergeEngine::try_merge: cannot read left vertex {}: {}",
                    v_left,
                    e,
                );
                return Ok(MergeOutcome::NoCrdtData);
            }
        };

        let right_content = match self.get_vertex_content(v_right) {
            Ok(c) => c,
            Err(e) => {
                log::debug!(
                    "SemanticMergeEngine::try_merge: cannot read right vertex {}: {}",
                    v_right,
                    e,
                );
                return Ok(MergeOutcome::NoCrdtData);
            }
        };

        // Step 3: Find the common ancestor vertex (the dead vertex both sides
        // replaced). Try the explicit `ancestor` field first, then fall back
        // to graph-based discovery using the `parent` field.
        let base_content = if let Some(ref ancestor) = group.ancestor {
            match self.get_vertex_content(ancestor) {
                Ok(c) => c,
                Err(e) => {
                    log::debug!(
                        "SemanticMergeEngine::try_merge: cannot read ancestor {}: {}",
                        ancestor,
                        e,
                    );
                    return Ok(MergeOutcome::NoCrdtData);
                }
            }
        } else if let Some(ref parent) = group.parent {
            match self.find_ancestor_content(parent, v_left.change, v_right.change) {
                Ok(Some(content)) => content,
                Ok(None) => {
                    log::debug!(