fileinfo, filetree, and Cogent Code should properly identify, treat generated files.

[rcoreilly]

Describe the feature

per https://github.com/golang/go/issues/13560 generated files are identified by a standard comment. fileinfo should check for this comment in .go files and set a "Generated" flag. Then filetree can style such files with an appropriate lighter text color (we use this for non-vcs files -- probably just re-use same and you can look at the file info to see which is which). Finally, Cogent Code will open such files with the texteditor set to read only, unless you open using the Edit filetree command.

Relevant code

No response