Add new module for storing build metadata (#593)

Add new module for storing build metadata

lib/build-data.sh

+# variable shared by this whole module
+BUILD_DATA_FILE=""
+
+bd_create() {
+  local cache_dir="$1"
+  BUILD_DATA_FILE="$cache_dir/build-data/node"
+  kv_create $BUILD_DATA_FILE
+}
+
+bd_get() {
+  kv_get $BUILD_DATA_FILE "$1"
+}
+
+bd_set() {
+  kv_set $BUILD_DATA_FILE "$1" "$2"
+}
+
+log_build_data() {
+  # print all values on one line in logfmt format
+  # https://brandur.org/logfmt
+  echo $(kv_list $BUILD_DATA_FILE)
+}

test/unit

@@ -148,6 +148,26 @@ testKeyValueNoFile() {
   assertEquals "$(kv_list $space)" ""
 }
 
+testBuildData() {
+  local cache_dir=$(mktemp -d)
+
+  bd_create $cache_dir
+
+  bd_set "test" "foo"
+  assertEquals "test=foo" "$(log_build_data)"
+
+  bd_set "test" "different-foo"
+  assertEquals "test=different-foo" "$(log_build_data)"
+
+  bd_set "foo" "value with spaces"
+  assertEquals "foo=\"value with spaces\" test=different-foo" "$(log_build_data)"
+
+  # values are printed with the keys sorted alphabetically
+  # this isn't required, and this test serves as documentation
+  bd_set "a" "this should come first"
+  assertEquals "a=\"this should come first\" foo=\"value with spaces\" test=different-foo" "$(log_build_data)"
+}
+
 # mocks
 source "$(pwd)"/test/mocks/stdlib.sh
 
@@ -155,6 +175,7 @@ source "$(pwd)"/test/mocks/stdlib.sh
 source "$(pwd)"/lib/monitor.sh
 source "$(pwd)"/lib/output.sh
 source "$(pwd)"/lib/kvstore.sh
+source "$(pwd)"/lib/build-data.sh
 
 # import the testing framework
 source "$(pwd)"/test/shunit2