Hidden Icon? files on macOS

For a while I've tolerated files named Icon? that appear in my console ls and git status output on macOS as well as in some IDE file trees like in Atom:

$ \ls -Al
total 696
-rw-------  1 micahsmith  staff  179 Nov 12  2019 Experiment Datasets.gsheet
-rw-r--r--@ 1 micahsmith  staff    0 Nov  2  2018 Icon?
-rw-------  1 micahsmith  staff  179 Aug 19  2018 test_20180818193120513976.gsheet
-rw-------  1 micahsmith  staff  179 Nov 12  2019 test_20180818193120513976_v1.gsheet

Why does the file Icon? appear and what is responsible for creating it? There is a nice discussion I found on superuser. The short answer is that in my case, the Google Drive desktop client ("Backup and Sync") for MacOS takes advantage of built-in Finder functionality to use a special icon for folders that are shared in Drive. The file that appears as Icon? is actually a "hidden file" with the icon image itself stored in a non-empty "resource fork".

Though the Superuser answer does not expand on this, the reason the literal carriage return character appears as a ? is because the default behavior of ls is equivalent to ls -q which sets:

Force printing of non-graphic characters in file names as the character '?'

I don't care about these details and I appreciate the integration with Drive, Dropbox, etc. with Finder. But I don't want these to show up in my console output.

Ignoring Icon? files in git status

Add to your global gitignore in ~/.gitignore:

Icon[^M]

Gitignore uses fnmatch syntax¹, so to match a literal carriage return character it can be enclosed within square brackets. To enter the literal carriage return character into Vim, for example, I use Ctrl k C R (see :help digraphs and :help digraph-table) which then appears as ^M.²

If you entered the literal Icon? into a .gitignore file, it would also hide this file, but only by accident, because the ? pattern matches any character, so the pattern would also match Iconz for example.

Ignoring Icon? files in ls -A

I couldn't figure out how to do this easily from man ls by modifying any ls aliases I have. But I decided that I can tolerate this as long as it does not show up in in git status output. Let me know if you figure out a good way to do this!