diff --git a/update_distfiles b/update_distfiles
index a61ba63c02..8b2fc316a8 100755
--- a/update_distfiles
+++ b/update_distfiles
@@ -10,6 +10,11 @@ SCRIPT_ROOT=$(dirname $(readlink -f "$0"))
 DEFINE_boolean dry_run ${FLAGS_FALSE} "Trial run, makes no changes."
 DEFINE_boolean upload ${FLAGS_FALSE} "Upload distfile mirror via gsutil."
 
+# FIXME(marineam): We need to add gs support to emirrordist so it
+# doesn't have to operate on a local copy of the complete mirror.
+DEFINE_boolean download ${FLAGS_FALSE} \
+    "Download the current mirror before making updates to it."
+
 MIRROR_ROOT="${DEFAULT_BUILD_ROOT}/mirror"
 UPLOAD_ROOT="gs://storage.core-os.net/mirror"
 
@@ -62,6 +67,28 @@ upload_mirror() {
     gsutil cp -a project-private \
         "${local_mirror}/info/*" "${remote_mirror}/info"
 }
+download_mirror() {
+    local repo_name="$1"
+    local local_mirror="${MIRROR_ROOT}/$repo_name"
+    local remote_mirror="${UPLOAD_ROOT}/$repo_name"
+
+    info "Downloading public distfiles for $repo_name"
+    mkdir -p "${local_mirror}/"{distfiles,info}
+    gsutil -m cp -n \
+        "${remote_mirror}/distfiles/*" "${local_mirror}/distfiles"
+
+    info "Downloading private metadata for $repo_name"
+    gsutil cp "${remote_mirror}/info/*" "${local_mirror}/info"
+}
+
+if [[ ${FLAGS_download} -eq ${FLAGS_TRUE} ]]; then
+    if [[ ! -f "$HOME/.boto" ]]; then
+        die_notrace "Please run gsutil config to create ~/.boto"
+    fi
+    for repo in "$@"; do
+        download_mirror "$repo"
+    done
+fi
 
 for repo in "$@"; do
     if ! portageq get_repo_path / "$repo" >/dev/null; then
@@ -70,6 +97,11 @@ for repo in "$@"; do
     update_local_mirror "$repo"
 done
 
+if [[ ${FLAGS_dry_run} == ${FLAGS_TRUE} ]]; then
+    info "Dry-run complete."
+    exit
+fi
+
 if [[ ${FLAGS_upload} -eq ${FLAGS_TRUE} ]]; then
     if [[ ! -f "$HOME/.boto" ]]; then
         die_notrace "Please run gsutil config to create ~/.boto"