Autocomplete in 'open file' works wrong with folders

This is related to what might also be a bug, where directories aren't displayed at the top when sorting files by name in the 'open file' dialogue. I think it used to work this way, but changed between Ubuntu 12.04 and 14.10.

So the fastest way to open files is often by typing. When an autocompleted folder name is displayed and is the only possible result for a path starting with those characters, pressing tab will cause the autocompleted text to be entered, while pressing enter normally causes the autocompleted folder to be navigated to.

If there is a file that starts starts with that folder's name in the same directory, the bug described in this report doesn't occur.

But if no such file exists, then if all files in the autocompleted folder start with the same letters, then pressing tab while the autocompleted folder's name is highlighted will cause those common letters to appear. Pressing enter instead of tab at the first step will instead cause a file to be opened with the name of those common letters.

The case where I encounter this bug is manual files for ffmpeg, which all start with 'ff' (and Ubuntu doesn't package ffmpeg which is why I'm opening them with gedit).

Autocompletion includes the '/' used to denote folders.

So, for example, in the folder /tmp/h, you have these files:
i
il
iif/
iiif/

In the 'open files' dialogue, if you type '/tmp/h', an autocompleted '/' appears. The expected behaviour is that if you press enter, you'll navigate to /tmp/h and view the files it contains. What actually happens is it opens '/tmp/h/i' for editing. Immediately after presseing enter while the autocompleted '/' is displayed, it turns a normal colour (instead of having autocompletion highlighting), an autocompleted 'i' appears, and the open file dialogue closes, having selected 'i' to open.

If there is also a file '/tmp/hi', then the '/' is not autocompleted, and pressing enter will just open the folder and display the letter 'i'. If, instead, there is a folder /tmp/h/uuu/ and a file /tmp/h/uuuuuuuu, and the folder uuu contains another folder u/ and a file uuuuuuuu, typing '/tmp/h/u' will cause an autocompleting 'uu' to be displayed (no '/' at the end), and pressing enter will just display the folder.

If the file /tmp/h/uuuuuuuu is removed or renamed to be shorter than uuu/, then instead of 'uu', 'uu/' will be autocompleted, and pressing enter will cause the folder /tmp/h/uuu/u/ to be opened, which is empty.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: gedit 3.10.4-0ubuntu6
ProcVersionSignature: Ubuntu 3.16.0-30.40-generic 3.16.7-ckt3
Uname: Linux 3.16.0-30-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.7-0ubuntu8.3
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Apr 16 01:32:26 2015
SourcePackage: gedit
UpgradeStatus: No upgrade log present (probably fresh install)