Failed to Show log from repository browser when that repository is located on a drive

What steps will reproduce the problem?

1. TortoiseGit -> Browse references
2. Select a local branch.
3. Right click -> Browse repository
4. Navigate to some subfolder.
5. Right click -> Show log

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

Expected: a log of the chosen reference, which can be limited to the selected path by unticking "Whole Project".

Actual:

Could not open log.
libgit reports:
/some/path/within/my/repository: '/some/path/within/my/repository' is outside repository

(Note that the path does literally start with a / and consists of the subpath within the repository only. In particular it is not a filesystem path and is not prefixed by the location of the clone.)

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

TortoiseGit 1.8.16.1 (C:\Program Files\TortoiseGit\bin) git version 2.5.3.windows.1 (20151231-c35ab9e4; C:\Program Files\Git\bin; C:\Program Files\Git\mingw64; C:\ProgramData\Git\config) Windows 8.1 x64

Please provide any additional information below.

Running "Show Log" directly from "Browse references" works as expected.