GTK File chooser search doesn't find files with a dot

(I'm not sure this is the correct package to file the bug against)

The (I assume) GTK 3.0 File chooser dialog doesn't allow searching files with a dot.

In the previous, but working, File chooser, in order to search files, the typeahead would be used. In order to search dotfiles (files starting with dot), one would enable display of hidden files if required, then just type the filename (starting with the dot character).

With the new search functionality, the dot character is not searched (or not considered valid, it's not clear), so one can't search dotfiles, and they need to manually go through the files in order to find the intended one(s).

In order to reproduce, for example:

- Open a webpage in Firefox
- Click "Save As..." on an image
- Tap Ctrl+H, if the hidden files are not displayed
- Tap Ctrl+F, in order to search
- Tap dot (`.`)

no files show.

I hope this is not another case of the (in)famous group of devs who's trying to reduce the whole desktop experience to a single blinking dot.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: libgtk-3-0 3.24.18-1ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-39.43-generic 5.4.41
Uname: Linux 5.4.0-39-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.3
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: MATE
Date: Mon Jul 27 15:52:53 2020
InstallationDate: Installed on 2020-07-01 (26 days ago)
InstallationMedia: Ubuntu-MATE 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: gtk+3.0
UpgradeStatus: No upgrade log present (probably fresh install)