Fix issues with Repository synchronization tool (#124)

* Only run tests in build/sync if directory exists

* Use t.Helper()

* Don't compare size of directories

* Fix TestFileHistory

* Fix linter issue

* Apply changes from https://github.com/mattermost/mattermost-plugin-github/pull/345

* Use ts file for tests

* Add sync target

Makefile

@@ -189,7 +189,9 @@ endif
 ifneq ($(HAS_WEBAPP),)
 	cd webapp && $(NPM) run test;
 endif
+ifneq ($(wildcard ./build/sync/plan/.),)
 	cd ./build/sync && $(GO) test -v $(GO_TEST_FLAGS) ./...
+endif
 
 ## Creates a coverage report for the server code.
 .PHONY: coverage
@@ -250,6 +252,15 @@ ifneq ($(HAS_WEBAPP),)
 endif
 	rm -fr build/bin/
 
+## Sync directory with a starter template
+sync:
+ifndef STARTERTEMPLATE_PATH
+	@echo STARTERTEMPLATE_PATH is not set.
+	@echo Set STARTERTEMPLATE_PATH to a local clone of https://github.com/mattermost/mattermost-plugin-starter-template and retry.
+	@exit 1
+endif
+	cd ${STARTERTEMPLATE_PATH} && go run ./build/sync/main.go ./build/sync/plan.yml $(PWD)
+
 # Help documentation à la https://marmelab.com/blog/2016/02/29/auto-documented-makefile.html
 help:
 	@cat Makefile build/*.mk | grep -v '\.PHONY' |  grep -v '\help:' | grep -B1 -E '^[a-zA-Z0-9_.-]+:.*' | sed -e "s/:.*//" | sed -e "s/^## //" |  grep -v '\-\-' | sed '1!G;h;$$!d' | awk 'NR%2{printf "\033[36m%-30s\033[0m",$$0;next;}1' | sort