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, 32 insertions, 0 deletions

diff --git a/internal/commitquery/context.go b/internal/commitquery/context.go
new file mode 100644
index 00000000..f39c32c8
--- /dev/null
+++ b/internal/commitquery/context.go
@@ -0,0 +1,32 @@
+// Package commitquery provides private commit-domain query routines.
+package commitquery
+
+import (
+	commitgraphread "codeberg.org/lindenii/furgit/format/commitgraph/read"
+	"codeberg.org/lindenii/furgit/objectid"
+	"codeberg.org/lindenii/furgit/objectstore"
+)
+
+// Context owns the mutable node arena for one commit query.
+type Context struct {
+	store objectstore.Store
+	graph *commitgraphread.Reader
+
+	nodes []node
+
+	byOID      map[objectid.ObjectID]NodeIndex
+	byGraphPos map[commitgraphread.Position]NodeIndex
+
+	markPhase uint32
+	touched   []NodeIndex
+}
+
+// NewContext builds one empty query context over one object store and optional commit-graph reader.
+func NewContext(store objectstore.Store, graph *commitgraphread.Reader) *Context {
+	return &Context{
+		store:      store,
+		graph:      graph,
+		byOID:      make(map[objectid.ObjectID]NodeIndex),
+		byGraphPos: make(map[commitgraphread.Position]NodeIndex),
+	}
+}