diff --git a/build-all b/build-all
index 4e381a6..6c513bf 100755
--- a/build-all
+++ b/build-all
@@ -1,9 +1,32 @@
 #!/usr/bin/env sh
 
 yes_retrieve() {
-    local a="$1"
+    local image="$1"
+    local ok=1
+    local out=
     shift || return
-    podman run -v="play":/out --rm --entrypoint /bin/busybox "$a" cp -- "$@" "/out/"
+    [ -d out ] || return
+    out="$(realpath out)" || return
+    for f in "$@"; do
+        local g="out/${f##*/}"
+        if [ -e "$g" ]; then
+            mv "$g" "$g~"
+        fi
+    done
+    podman run -v="$out":/out --rm --entrypoint /bin/busybox "$image" \
+      cp -- "$@" "/out/" || return
+    for f in "$@"; do
+        local g="out/${f##*/}"
+        if [ -e "$g" ]; then
+            if [ -e "$g~" ]; then
+                rm "$g~"
+            fi
+        else
+            printf '%s: %s\n' yes_retrieve "failed to copy file $f to $g"
+            ok=0
+        fi
+    done
+    [ $ok = 1 ]
 }
 
 dbg_retrieve() {
@@ -14,9 +37,10 @@ dbg_retrieve() {
 }
 
 : \
- && cd "$(readlink -f "$0")" \
+ && me="$(readlink -f "$0")" \
+ && cd "${me%/*}" \
 \
- && [ -d out ] || mkdir out \
+ && { [ -d out ] || mkdir out ;} \
 \
  && podman build -t notwa-util notwa-util \
  && podman build -t cosmo cosmo \