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, 67 insertions, 0 deletions

diff --git a/internal/commitquery/marks.go b/internal/commitquery/marks.go
new file mode 100644
index 00000000..f88fdf25
--- /dev/null
+++ b/internal/commitquery/marks.go
@@ -0,0 +1,67 @@
+package commitquery
+
+// Marks returns the mark bits of one internal node.
+func (ctx *Context) Marks(idx NodeIndex) markBits {
+	return ctx.nodes[idx].marks
+}
+
+// HasAnyMarks reports whether one internal node has any requested bit.
+func (ctx *Context) HasAnyMarks(idx NodeIndex, bits markBits) bool {
+	return ctx.nodes[idx].marks&bits != 0
+}
+
+// HasAllMarks reports whether one internal node already has all requested bits.
+func (ctx *Context) HasAllMarks(idx NodeIndex, bits markBits) bool {
+	return ctx.nodes[idx].marks&bits == bits
+}
+
+// SetMarks ORs one set of mark bits into one internal node.
+func (ctx *Context) SetMarks(idx NodeIndex, bits markBits) {
+	newBits := bits &^ ctx.nodes[idx].marks
+	if newBits == 0 {
+		return
+	}
+
+	ctx.trackTouched(idx)
+	ctx.nodes[idx].marks |= bits
+}
+
+// ClearMarks removes one set of mark bits from one internal node.
+func (ctx *Context) ClearMarks(idx NodeIndex, bits markBits) {
+	if ctx.nodes[idx].marks&bits == 0 {
+		return
+	}
+
+	ctx.trackTouched(idx)
+	ctx.nodes[idx].marks &^= bits
+}
+
+// BeginMarkPhase starts one tracked mark-mutation phase.
+func (ctx *Context) BeginMarkPhase() {
+	ctx.markPhase++
+	if ctx.markPhase == 0 {
+		ctx.markPhase++
+		for i := range ctx.nodes {
+			ctx.nodes[i].touchedPhase = 0
+		}
+	}
+
+	ctx.touched = ctx.touched[:0]
+}
+
+// ClearTouchedMarks clears the provided bits from all nodes touched in the
+// current mark phase.
+func (ctx *Context) ClearTouchedMarks(bits markBits) {
+	for _, idx := range ctx.touched {
+		ctx.nodes[idx].marks &^= bits
+	}
+}
+
+func (ctx *Context) trackTouched(idx NodeIndex) {
+	if ctx.nodes[idx].touchedPhase == ctx.markPhase {
+		return
+	}
+
+	ctx.nodes[idx].touchedPhase = ctx.markPhase
+	ctx.touched = append(ctx.touched, idx)
+}