message: guix: Allow changing the base manifest in guix-verify
  When verifying guix attestations, it is useful to set a particular
  signer's manifest as the base to compare against.
diff: @@ -28,7 +28,11 @@ cmd_usage() {
  cat <<EOF
  Synopsis:
  - env GUIX_SIGS_REPO=<path/to/guix.sigs> ./contrib/guix/guix-verify
  + env GUIX_SIGS_REPO=<path/to/guix.sigs> [ SIGNER=<signer> ] ./contrib/guix/guix-verify
  +
  +Example overriding signer's manifest to use as base
  +
  + env GUIX_SIGS_REPO=/home/dongcarl/guix.sigs SIGNER=achow101 ./contrib/guix/guix-verify
  EOF
  }
  @@ -92,6 +96,17 @@ echo "--------------------"
  echo ""
  if (( ${#all_noncodesigned[@]} )); then
  compare_noncodesigned="${all_noncodesigned[0]}"
  + if [[ -n "$SIGNER" ]]; then
  + signer_noncodesigned="$OUTSIGDIR_BASE/$SIGNER/noncodesigned.SHA256SUMS"
  + if [[ -f "$signer_noncodesigned" ]]; then
  + echo "Using $SIGNER's manifest as the base to compare against"
  + compare_noncodesigned="$signer_noncodesigned"
  + else
  + echo "Unable to find $SIGNER's manifest, using the first one found"
  + fi
  + else
  + echo "No SIGNER provided, using the first manifest found"
  + fi
  for current_manifest in "${all_noncodesigned[@]}"; do
  verify "$compare_noncodesigned" "$current_manifest"
  @@ -112,6 +127,17 @@ echo "--------------------"
  echo ""
  if (( ${#all_all[@]} )); then
  compare_all="${all_all[0]}"
  + if [[ -n "$SIGNER" ]]; then
  + signer_all="$OUTSIGDIR_BASE/$SIGNER/all.SHA256SUMS"
  + if [[ -f "$signer_all" ]]; then
  + echo "Using $SIGNER's manifest as the base to compare against"
  + compare_all="$signer_all"
  + else
  + echo "Unable to find $SIGNER's manifest, using the first one found"
  + fi
  + else
  + echo "No SIGNER provided, using the first manifest found"
  + fi
  for current_manifest in "${all_all[@]}"; do
  verify "$compare_all" "$current_manifest"
  