$ git --version --build-options
git version 2.11.1.windows.1
built from commit: 1c1842bcba45569a84112ec64f72b08eb2d57c68
sizeof-long: 4
machine: x86_64
$ cmd.exe /c ver
Microsoft Windows [Version 6.3.9600]
Path Option: Cmd
SSH Option: OpenSSH
CRLF Option: CRLFCommitAsIs
Bash Terminal Option: MinTTY
Performance Tweaks FSCache: Enabled
Use Credential Manager: Enabled
Enable Symlinks: Enabled
Enable Builtin Difftool: Disabled
(same as in 2.11.0)
German Windows
gitconfig contains
[i18n]
logoutputencoding = Windows-1252
which used to work in 2.11.0 and does not in 2.11.1
PowerShell
git log --oneline


git init
echo "testfile" > b盲盲盲盲.txt
git add .
git commit -m "a盲 o枚 u眉 s脽 - all broken now"
git log --oneline --stat

I believe Issue #945 and its compatriots covers this. the latest prerelease includes a fix. https://github.com/git-for-windows/git/releases/tag/v2.11.1.windows-prerelease.2 (the sort order on the release page doesn't quite get it right ;-)
Also check for your LC settings.
No, not really. The prerelease behaves exactly like the release
git version 2.11.1.windows.prerelease.2
built from commit: 86d49ccac7afb39e03ba2632803c5ab67d4bb792
sizeof-long: 4
machine: x86_64
Tried to set LC_ALL=C, does not make any difference either
Tried some older versions, the issue must have been introduced somewhere between
git version 2.11.0.windows.1 (does not print a commit id) and
git version 2.11.0.windows.2 (not working any more)
built from commit: 9e46438a63c7991eb394fb752fa0ccf2eb63e248
Note beyond: maybe the file name output never worked correctly, did not notice that, because we don't use non-ascii characters for file names :-)

@Snaptags Try export LC_ALL=de_DE. Also make sure your logoutputencoding, your locale settings and mintty text settings (set Options->Text->Character set to CP1252) all match.
Setting an environment variable LC_ALL with content de_DE seems to fix the issue, thanks a lot!
@Snaptags That's good news! If you want to see your paths as well, try git config core.quotepath off, characters outside the ASCII range get quoted by default.

That's just differently wrong :-)
But I hardly have any file names with non ASCII-characters, so I don't care :-)
Ah, yes, of course, the path is UTF-8 and you're using Windows-1252 for text. Nevermind then :)
Went back to LC_ALL=C. Better to have ugly git logs than MILLIONS of Perl warnings about how the locale could not be set.
adding --encoding to the log call is a partly solution. It doesn't really matter WHAT you set the encoding to, actually. Very strange:
git log --oneline --stat --encoding=wtf

Most helpful comment
@Snaptags Try
export LC_ALL=de_DE. Also make sure your logoutputencoding, your locale settings and mintty text settings (set Options->Text->Character set to CP1252) all match.