The console shows the following error, so that's probably where I'll start debugging:
Error in response to storage.get: TypeError: Cannot read property 'innerText' of null
at reorderFiles (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/content.js:53:50)
at trigger (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/content.js:118:2)
at window.gitHubInjection (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/content.js:142:4)
at gitHubInjection (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/node_modules/github-injection/index.js:39:3)
at window.HideFilesOnGitHub.storage.get (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/content.js:140:10)
at Object.window.chrome.storage.sync.get.items [as callback] (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/api.js:13:7)
at Object.get (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/api.js:12:33)
at HTMLDocument.document.addEventListener (chrome-extension://nafjgigppkofohfmllnkoablobneemnc/content.js:133:35)
I'm loading the unpacked extension at commit https://github.com/sindresorhus/hide-files-on-github/commit/f0da7c60f96d0c044701d8445af293ccac219a72, and when I visit https://github.com/EFForg/https-everywhere/tree/24338b1e7a3d136023bb91600be9587e1ba55f97, I see that several of the files aren't visible at all, even when showing the dotfiles. Here are some screenshots to illustrate:
Without extension loaded:
With extension loaded:
The console shows the following error, so that's probably where I'll start debugging: