Urgh I made some wrong amends and I'm too tired to separate the commits out this time

ancestor: Split out of reachability
mergebase: Add merge base routines
internal/commitquery: Add commit query context engine thingy
internal/peel: Shared tag peeling
errors: Shared object query errors
internal/testgit: Add rooted repo helpers; remove raw path access
objectstore/memory: Add in-memory object store
objectid: Add Compare helper

1 files changed, 107 insertions, 0 deletions

diff --git a/internal/commitquery/graph_pos.go b/internal/commitquery/graph_pos.go
new file mode 100644
index 00000000..2031e3d8
--- /dev/null
+++ b/internal/commitquery/graph_pos.go
@@ -0,0 +1,107 @@
+package commitquery
+
+import commitgraphread "codeberg.org/lindenii/furgit/format/commitgraph/read"
+
+// ResolveGraphPos resolves one commit-graph position to one internal query node.
+func (ctx *Context) ResolveGraphPos(pos commitgraphread.Position) (NodeIndex, error) {
+	idx, ok := ctx.byGraphPos[pos]
+	if ok {
+		err := ctx.ensureLoaded(idx)
+		if err != nil {
+			return 0, err
+		}
+
+		return idx, nil
+	}
+
+	commit, err := ctx.graph.CommitAt(pos)
+	if err != nil {
+		return 0, err
+	}
+
+	idx, ok = ctx.byOID[commit.OID]
+	if !ok {
+		idx = ctx.newNode(commit.OID)
+		ctx.byOID[commit.OID] = idx
+	}
+
+	ctx.byGraphPos[pos] = idx
+	ctx.nodes[idx].graphPos = pos
+	ctx.nodes[idx].hasGraphPos = true
+
+	err = ctx.loadCommitAtGraphPos(idx, pos)
+	if err != nil {
+		delete(ctx.byGraphPos, pos)
+
+		return 0, err
+	}
+
+	return idx, nil
+}
+
+// loadByGraphPos populates one node from a commit-graph position.
+func (ctx *Context) loadByGraphPos(idx NodeIndex) error {
+	pos := ctx.nodes[idx].graphPos
+
+	return ctx.loadCommitAtGraphPos(idx, pos)
+}
+
+func (ctx *Context) loadCommitAtGraphPos(idx NodeIndex, pos commitgraphread.Position) error {
+	commit, err := ctx.graph.CommitAt(pos)
+	if err != nil {
+		return err
+	}
+
+	parents := make([]Parent, 0, 2+len(commit.ExtraParents))
+
+	if commit.Parent1.Valid {
+		parentOID, err := ctx.graph.OIDAt(commit.Parent1.Pos)
+		if err != nil {
+			return err
+		}
+
+		parents = append(parents, Parent{
+			ID:          parentOID,
+			GraphPos:    commit.Parent1.Pos,
+			HasGraphPos: true,
+		})
+	}
+
+	if commit.Parent2.Valid {
+		parentOID, err := ctx.graph.OIDAt(commit.Parent2.Pos)
+		if err != nil {
+			return err
+		}
+
+		parents = append(parents, Parent{
+			ID:          parentOID,
+			GraphPos:    commit.Parent2.Pos,
+			HasGraphPos: true,
+		})
+	}
+
+	for _, parentPos := range commit.ExtraParents {
+		parentOID, err := ctx.graph.OIDAt(parentPos)
+		if err != nil {
+			return err
+		}
+
+		parents = append(parents, Parent{
+			ID:          parentOID,
+			GraphPos:    parentPos,
+			HasGraphPos: true,
+		})
+	}
+
+	data := Commit{
+		ID:            commit.OID,
+		Parents:       parents,
+		CommitTime:    commit.CommitTimeUnix,
+		Generation:    commit.GenerationV2,
+		HasGeneration: commit.GenerationV2 != 0,
+		GraphPos:      pos,
+		HasGraphPos:   true,
+	}
+
+	return ctx.populateNode(idx, data)
+}