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, 25 insertions, 0 deletions

diff --git a/internal/commitquery/compare.go b/internal/commitquery/compare.go
new file mode 100644
index 00000000..748ef712
--- /dev/null
+++ b/internal/commitquery/compare.go
@@ -0,0 +1,25 @@
+package commitquery
+
+import "codeberg.org/lindenii/furgit/objectid"
+
+// Compare compares two internal nodes using merge-base queue ordering.
+func (ctx *Context) Compare(left, right NodeIndex) int {
+	leftGeneration := ctx.EffectiveGeneration(left)
+	rightGeneration := ctx.EffectiveGeneration(right)
+
+	switch {
+	case leftGeneration < rightGeneration:
+		return -1
+	case leftGeneration > rightGeneration:
+		return 1
+	}
+
+	switch {
+	case ctx.nodes[left].commitTime < ctx.nodes[right].commitTime:
+		return -1
+	case ctx.nodes[left].commitTime > ctx.nodes[right].commitTime:
+		return 1
+	}
+
+	return objectid.Compare(ctx.nodes[left].id, ctx.nodes[right].id)
+}