Processing of getProjectFiles() (and ignore patterns) needs revision

[PopGoesTheWza]

Working on "simple" PR #693 , I found out current getProjectFiles() processing is very inefficient

Expected Behavior

getProjectFiles() should:

• ignore dotted folders like .git
• limit its recursive search for legitimate/valid files (i.e. appsscript.json, .gs, .js, .ts and .html
• (optional) the support .claspignore should work as standard .ignore files (i.e. node_modules should suffice instead of current **/node_modules/** goofy syntax)

Actual Behavior

getProjectFiles() first grabs every files from any subfolder from rootDir before trying any .claspignore pattern. this includes any usually ignored folders like .git
Next .claspignore patterns are applied in a way that does not allow the use of standard notation (i.e. node_modules must be express as **/node_modules/**

Steps to Reproduce the Problem

1. add dummy .clasp.json and appsscript.json and an empty (no pattrens) .claspignore
2. run clasp status

Specifications

• Node version (node -v): 10.16.3
• Version (clasp -v): 2.2.1
• OS (Mac/Linux/Windows): Mac OS

[PopGoesTheWza]

Maybe it would be sensible to rely on solid 3rd party package to handle this part. This one looks like a serious candidate https://www.npmjs.com/package/ignore