allow multi-node push and imagetools to use custom registry config

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

vendor/github.com/moby/buildkit/cmd/buildkitd/config/gcpolicy.go

@@ -0,0 +1,31 @@
+package config
+
+const defaultCap int64 = 2e9 // 2GB
+
+func DefaultGCPolicy(p string, keep int64) []GCPolicy {
+	if keep == 0 {
+		keep = DetectDefaultGCCap(p)
+	}
+	return []GCPolicy{
+		// if build cache uses more than 512MB delete the most easily reproducible data after it has not been used for 2 days
+		{
+			Filters:      []string{"type==source.local,type==exec.cachemount,type==source.git.checkout"},
+			KeepDuration: 48 * 3600, // 48h
+			KeepBytes:    512 * 1e6, // 512MB
+		},
+		// remove any data not used for 60 days
+		{
+			KeepDuration: 60 * 24 * 3600, // 60d
+			KeepBytes:    keep,
+		},
+		// keep the unshared build cache under cap
+		{
+			KeepBytes: keep,
+		},
+		// if previous policies were insufficient start deleting internal data to keep build cache under cap
+		{
+			All:       true,
+			KeepBytes: keep,
+		},
+	}
+}