* Restrict repository indexing by file extension
* Use REPO_EXTENSIONS_LIST_INCLUDE instead of REPO_EXTENSIONS_LIST_EXCLUDE and have a more flexible extension pattern
* Corrected to pass lint gosimple
* Add wildcard support to REPO_INDEXER_EXTENSIONS
* This reverts commit 72a650c8e4.
* Add wildcard support to REPO_INDEXER_EXTENSIONS (no make vendor)
* Simplify isIndexable() for better clarity
* Add gobwas/glob to vendors
* manually set appengine new release
* Implement better REPO_INDEXER_INCLUDE and REPO_INDEXER_EXCLUDE
* Add unit and integration tests
* Update app.ini.sample and reword config-cheat-sheet
* Add doc page and correct app.ini.sample
* Some polish on the doc
* Simplify code as suggested by @lafriks
