Prepare Travis CI for web3.js and explorer

.travis/export-github-repo.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+#
+# Exports a subdirectory into another github repository
+#
+
+set -e
+if [[ -z $GITHUB_TOKEN ]]; then
+  echo GITHUB_TOKEN not defined
+  exit 1
+fi
+
+cd "$(dirname "$0")/.."
+
+pip3 install git-filter-repo
+
+declare subdir=$1
+declare repo_name=$2
+
+[[ -n $subdir ]] || {
+  echo "Error: subdir not specified"
+  exit 1
+}
+[[ -n $repo_name ]] || {
+  echo "Error: repo_name not specified"
+  exit 1
+}
+
+.travis/affects.sh "^$subdir/" || exit 0
+echo "Exporting $subdir"
+
+set -x
+rm -rf .github_export/"$repo_name"
+git clone https://${GITHUB_TOKEN}@github.com/solana-labs/"$repo_name" .github_export/"$repo_name"
+
+# TODO: Try using `--refs $TRAVIS_COMMIT_RANGE` to speed up the filtering
+git filter-repo --subdirectory-filter "$subdir" --target .github_export/"$repo_name"
+
+git -C .github_export/"$repo_name" push https://${GITHUB_TOKEN}@github.com/solana-labs/"$repo_name"