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, 42 insertions, 0 deletions

diff --git a/internal/commitquery/populate.go b/internal/commitquery/populate.go
new file mode 100644
index 00000000..87d65bf8
--- /dev/null
+++ b/internal/commitquery/populate.go
@@ -0,0 +1,42 @@
+package commitquery
+
+import "fmt"
+
+// populateNode fills one node's metadata and resolves its parents.
+func (ctx *Context) populateNode(idx NodeIndex, commit Commit) error {
+	if ctx.nodes[idx].loaded {
+		if ctx.nodes[idx].id != commit.ID {
+			return fmt.Errorf("commitquery: node identity mismatch: have %s, got %s", ctx.nodes[idx].id, commit.ID)
+		}
+
+		return nil
+	}
+
+	ctx.nodes[idx].id = commit.ID
+	ctx.nodes[idx].commitTime = commit.CommitTime
+	ctx.nodes[idx].generation = commit.Generation
+	ctx.nodes[idx].hasGeneration = commit.HasGeneration
+
+	if commit.HasGraphPos {
+		ctx.nodes[idx].graphPos = commit.GraphPos
+		ctx.nodes[idx].hasGraphPos = true
+		ctx.byGraphPos[commit.GraphPos] = idx
+	}
+
+	ctx.nodes[idx].loaded = true
+	ctx.nodes[idx].parents = ctx.nodes[idx].parents[:0]
+
+	for _, parent := range commit.Parents {
+		parentIdx, err := ctx.resolveParent(parent)
+		if err != nil {
+			ctx.nodes[idx].loaded = false
+			ctx.nodes[idx].parents = nil
+
+			return err
+		}
+
+		ctx.nodes[idx].parents = append(ctx.nodes[idx].parents, parentIdx)
+	}
+
+	return nil
+}