Add script to fetch non-Apache-2.0 licenses from dependencies

LICENSES/fetch-licenses.sh

@@ -0,0 +1,71 @@
+#!/bin/bash -u
+#
+# Requires license-detector from https://github.com/go-enry/go-license-detector/releases/tag/v4.3.0 
+# to be installed in the current directory.
+
+function cleanup {
+  rm  -rf tmp
+}
+trap cleanup EXIT
+
+check_manually=""
+exceptions="github.com/opencontainers/go-digest" # Apache2.0 but reported as CC-BY-SA-4.0
+
+dirs=$(grep -E '^[[:blank:]]+.+\..+/.+' ../go.mod | awk '{print $1}')
+
+for dir_versioned in $dirs; do
+  found="no"
+  for except in $exceptions; do
+    if [ $except == "$dir_versioned" ]; then found="yes"; break; fi
+  done
+  if [ "$found" == "yes" ]; then continue; fi
+
+  echo $dir_versioned":"
+  dir=$dir_versioned
+
+  # versioned paths can not be used by the license-detector
+  if [[ $dir =~ /v[0-9]$ ]]; then
+    dir=${dir%/*}
+  fi
+
+  if [ -n "${dir%%github.com*}" ]; then
+    repo=$(curl -Ls "https://$dir?go-get=1" | xml2 2>/dev/null | grep -E '/meta/@content=.+\..+ git ' | awk '{print $3}')
+  else
+    # e.g. github.com/moby/sys/user -> github.com/moby/sys
+    repo_dir=$(echo $dir|cut -d'/' -f1-3)
+    repo="https://$repo_dir"
+  fi
+  echo "  $repo"
+
+  json=$(./license-detector $repo -f json)
+  license=$(echo $json | jq -r '.[0].matches[0].license')
+  if [ "$license" == "null" ]; then
+    echo "  No license found, check manually"
+    check_manually="$check_manually $repo"
+    continue
+  fi
+  if [ "$license" == "Apache-2.0" ]; then
+    echo "  Apache-2.0 --> no copy required"
+    continue
+  fi
+
+  file=$(echo $json | jq -r '.[0].matches[0].file')
+  if [ "$file" == "null" ]; then
+    echo "  No file found, check manually" 
+    check_manually="$check_manually $repo"
+    continue
+   fi
+
+  echo "  license=$license, file=$file"
+  rm -rf tmp
+  git clone -q --depth=1 "$repo" tmp
+  mkdir -p "$dir_versioned"
+  cp "tmp/$file" "$dir_versioned/"
+  rm -rf tmp
+done
+
+if [ "$check_manually" == "" ]; then exit 0; fi
+
+echo
+echo "Please check these dependencies manually:"
+echo $check_manually | tr ' ' '\n'