Ref: https://github.com/git/git/commit/556e68032f8248c831e48207e5cb923c9fe0e42c If GIT_FLUSH=true, it should mean to "do the flush". But that commit made skip_stdout_flush=true when GIT_FLUSH=true. And by the way, only accepting GIT_FLUSH=true is quite breaking, it drops the compatibility of GIT_FLUSH=1: it causes the existing programs which depend on the "flushing(GIT_FLUSH=1)" behavior would hang forever if they use the new git binary, because the program won't see any flushed output ....
