Icon overlay show ignored directories containing files as modified

What steps will reproduce the problem?

1. Create a new empty repository.
2. Create a .gitignore with the content subdir/
3. Create the subdir/ directory.
4. Create testfile under subdir/

What is the expected output? What do you see instead?

Tortoisegit diff will show .gitignore as unversioned and subdir/testfile as ignored.

git status agrees on .gitignore but shows subdir/ as ignored instead of subdir/testfile, which isn't show at all:

$ git status --ignored
On branch master

No commits yet

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        .gitignore

Ignored files:
  (use "git add -f <file>..." to include in what will be committed)

        subdir/

nothing added to commit but untracked files present (use "git add" to track)

Icon overlay of subdir/testfile is missing, which is expected since the file is ignored.

Icon overlay of subdir/ shows as modified (red icon with !), which is unexpected since it's ignored.

What I expect is the icon overlay of subdir/ to be missing too, since the directory is ignored.

What version of TortoiseGit and Git are you using? On what operating system?

TortoiseGit 2.5.0.0

git version 2.14.1.windows.1

Windows 7 Enterprise SP1, 64bit

Please provide any additional information below.

Using the pattern subdir/* or subdir/** in .gitignore has the expected behavior.