On Wed, Sep 13, 2017 at 01:59:17PM +0200, demerphq wrote: > After being away for a while I saw the following message in one of my git repos: > > $ git status > On branch yves/xxx > Your branch is based on 'origin/yves/xxx', but the upstream is gone. > (use "git branch --unset-upstream" to fixup) > > nothing to commit, working tree clean > $ git branch --unset-upstream > fatal: could not unset 'branch.yves/simple_projection.merge' Hrm. I wonder what caused this failure. The error would be in git_config_set_multivar_in_file_gently(). Most errors there produce another error message before hitting the die(). In fact, the only case I see where it would not produce another message is if it found nothing to unset (but in that case, "branch" would never have called the function in the first place). > At this point my .git/config file was empty, and all of my config was lost. > > I assume that things that rewrite .git/config do not check for a > successful write before deleting the old version of the file. No, it writes the new content to "config.lock" and then renames it into place. All of the write() calls to the temporary file are checked. The old data is copied over after having been ready by mmap (which is also error-checked). Given that your output is consistent with it failing to find the key, and that the result is an empty file, it sounds like somehow the mmap'd input appeared empty (but neither open nor fstat nor mmap returned an error). You're not on any kind of exotic filesystem, are you? -Peff
