Problem: pbuilder uses tar, which results in "Cannot readlink: Invalid argument"

The issue is present on podman hosts when they are themslves KVM guests, but
is not present if podman is used on host OS, which iteself is installed on
bare metal.

Solution: create `faketar` script and patch pbuilder to use it instead of tar.
The `faketar` script uses simple `cp` and `mv` commands, which not only help
us avoid the issue with `tar`, but also make our builds faster by skipping
compression & decompression of tgz.

Due to a rather esoteric nature of the problem `faketar` script is reasonable
workaround, which also saves on build time.

Author: qount25

lib/pgpm/deb/Dockerfile

@@ -7,7 +7,7 @@
 # { "builder": {"Entitlements": {"security-insecure": true }} }
 # ```
 # ```
-# DOCKER_BUILDKIT=1 docker build --allow security.insecure -t IMAGE_NAME /path/to/pgpm
+# DOCKER_BUILDKIT=1 docker build --allow security.insecure -t IMAGE_NAME .
 # ```
 
 # This Dockerfile is used to build a Debian image, which includes pbuilder and
@@ -21,8 +21,12 @@ MAINTAINER PGPM Debian Maintainer debian.maintainer@postgres.pm
 VOLUME /proc
 ARG DEBIAN_FRONTEND=noninteractive
 RUN apt update
-RUN apt install -y build-essential pbuilder fakeroot fakechroot
+RUN apt install -y build-essential pbuilder fakeroot fakechroot vim ripgrep
 RUN echo 'MIRRORSITE=http://deb.debian.org/debian'  > /etc/pbuilderrc
 RUN echo 'AUTO_DEBSIGN=${AUTO_DEBSIGN:-no}'         > /root/.pbuilderrc
 RUN echo 'HOOKDIR=/var/cache/pbuilder/hooks'       >> /root/.pbuilderrc
-RUN --security=insecure pbuilder create
+COPY scripts/faketar /usr/bin/
+RUN chmod +x /usr/bin/faketar
+RUN sed -E -i "s/local TAR=tar/local TAR=faketar/" /usr/lib/pbuilder/pbuilder-modules
+RUN sed -E -i "s/if [!] tar -c --use-compress-program/if ! faketar -c --use-compress-program/" /usr/lib/pbuilder/pbuilder-modules
+RUN --security=insecure fakeroot pbuilder create

lib/pgpm/deb/builder.rb

@@ -14,7 +14,6 @@ def initialize(spec)
       def build
         prepare_image
         start_container
-        patch_pbuilder
 
         prepare_versioned_source
         generate_deb_src_files(:versioned)
@@ -127,9 +126,12 @@ def prepare_image
 
       def build_local_image
           puts "  Building local #{image_name}..."
-          system("podman create -it --privileged --tmpfs /tmp --name pgpm-deb-tmp #{base_image_name}")
+          container_opts = "-it --privileged --tmpfs /tmp --name pgpm-deb-tmp"
+          system("podman create #{container_opts} #{base_image_name}")
           system("podman start pgpm-deb-tmp")
 
+          patch_pbuilder
+
           # Generate pbuilder_install script.sh, copy it inside the image
           pbuild_install_script_path = "#{@pgpm_dir}/pbuilder_install_script.sh"
           puts "  Generating #{pbuild_install_script_path}..."
@@ -194,7 +196,9 @@ def start_container
       # a result.
       def patch_pbuilder
         cmd = "sed -E -i \"s/(^function clean_subdirectories.*$)/\\1\\n  return/g\" /usr/lib/pbuilder/pbuilder-modules"
-        system("podman exec #{@container_name} /bin/bash -c '#{cmd}'")
+        system("podman exec pgpm-deb-tmp /bin/bash -c '#{cmd}'")
+        cmd = "sed -E -i \"s/if [[] [!] -f [\\\"]([$]BASETGZ)/if [ ! -d \\\"\\1/\" /usr/lib/pbuilder/pbuilder-modules"
+        system("podman exec pgpm-deb-tmp /bin/bash -c '#{cmd}'")
       end
 
       def run_build(pkg_type = :versioned)

lib/pgpm/deb/scripts/faketar

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+ARGS="$@"
+echo "faketar ${ARGS[@]}"
+
+if [[ " ${ARGS[*]} " =~ [[:space:]]-x[[:space:]] ]]; then # compress
+  # Replacing this command:
+  #     tar -x -p -f "$BASETGZ"
+  src="$4"
+  echo "Copying $src/* to $(pwd)"
+  cp -pur $src/* ./
+elif [[ " ${ARGS[*]} " =~ [[:space:]]-c[[:space:]] ]]; then # extract
+  # Replacing this command:
+  #     tar -c --use-compress-program "$COMPRESSPROG" -f "${BASETGZ}.tmp" ./*
+  target="$5"
+  src="."
+  mkdir $target
+  echo "Moving $src/* to $target/"
+  mv $src/* $target/
+  # Remove existing directory into which we move the contents.
+  # Otherwise, pbuilder (when it calls `mv`) will move $target inside it,
+  # instead of copying $target/* into it.
+  if [[ -d "${target%".tmp"}" ]]; then
+    rm -rf "${target%".tmp"}"
+  fi
+fi