config_file: Don't crash on options without a section

[nelhage]

Found via fuzzing.

[ethomson]

Nice find - but git seems to parse configuration values without a section just fine. I think that actually we should:

if (current_section) {
    git_buf_puts(&buf, current_section);
    git_buf_putc(&buf, '.');
}

for (c = var_name; *c; c++)
    git_buf_putc(&buf, git__tolower(*c));

[nelhage]

Huh, I found that if I added hi = 0 to my .git/config, I get

[nelhage@penguin:~/code/libgit2]$ git status
error: key does not contain a section: hi

That said, it doesn't seem to stop parsing at the error, which I believe this patch does. I'm happy to accept your proposal.

[ethomson]

I suspected it might be a warning with some commands. (git config —list did not warn, but that was the extent of what I ran.)

Would you mind throwing a comment in that suggests that we should warn too? Once warnings land we can wire it up.

Thanks!

[pks-t]

I'm not sure at all what happens in case we parse a config key without section. Could you please add a test that demonstrates that we do not fail at another place and that demonstrates what's expected to happen?

[pks-t]

Thanks for your fix and the test!