pipe is returning empty string in bash in git for windows

Question

Edit: Issue has been resolved after update to Git for Windows >= 2.9.0.windows1

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Disclaimer

Some comments are referring to full \"story\" behind this is

Answer 1

Summarizing the comments, the short (tl;dr) version: either downgrade, upgrade, and/or re-install MSYS and MinGW that come with Git for Windows.

MSYS supplements MinGW, and the version provided by Git for Windows may be modified from the original maintainers of MSYS. There was a bug reported against MSYS for what appears to be this same issue (using "mingw version: 64 bit bundled with git version 2.8.3.windows.1"), but was marked as "works for me" (i.e., "can't reproduce"). But there was a comment that the problem could be in the repackaging:

"Please be advised that MSYS, as bundled with git for windows, may be modified from our official distribution, (and 64-bit MinGW certainly isn't ours); thus we don't formally support either of these." https://sourceforge.net/p/mingw/bugs/2303/

Long story short, looks like a bug.