Merge pull request #18896 from tboettch/dockerToolsFix

dockerTools: Fix layer redundancy.

pkgs/build-support/docker/default.nix

···
 { stdenv, lib, callPackage, runCommand, writeReferencesToFile, writeText, vmTools, writeScript
-, docker, shadow, utillinux, coreutils, jshon, e2fsprogs, go, pigz }:
+, docker, shadow, utillinux, coreutils, jshon, e2fsprogs, go, pigz, findutils }:
 
 # WARNING: this API is unstable and may be subject to backwards-incompatible changes in the future.
   
···
                then mkPureLayer { inherit baseJson contents extraCommands; }
                else mkRootLayer { inherit baseJson fromImage fromImageName fromImageTag contents runAsRoot diskSize extraCommands; });
       result = runCommand "${baseName}.tar.gz" {
-        buildInputs = [ jshon pigz ];
+        buildInputs = [ jshon pigz coreutils findutils ];
 
         imageName = name;
         imageTag = tag;
···
           buildArgs = args;
         };
       } ''
+        # Print tar contents:
+        # 1: Interpreted as relative to the root directory
+        # 2: With no trailing slashes on directories
+        # This is useful for ensuring that the output matches the values generated by the "find" command
+        ls_tar() {
+            for f in $(tar -tf $1 | xargs realpath -ms --relative-to=.); do
+                if [ "$f" != "." ]; then
+                    echo "/$f"
+                fi
+            done
+        }
+      
         mkdir image
         touch baseFiles
         if [ -n "$fromImage" ]; then
···
           parentID=$(jshon -e $fromImageName -e $fromImageTag -u < image/repositories)
           
           for l in image/*/layer.tar; do
-            tar -tf $l >> baseFiles
+            ls_tar $l >> baseFiles
           done
         fi
 
···
         fi
 
         echo Adding layer
-        tar -tf temp/layer.tar >> baseFiles
-        sed 's/^\.//' -i baseFiles
+        ls_tar temp/layer.tar >> baseFiles
         comm <(sort -u baseFiles) <(sort -u layerFiles) -1 -3 > newFiles
         tar -rpf temp/layer.tar --mtime=0 --no-recursion --files-from newFiles 2>/dev/null || true