tests: use 'test_must_be_empty' instead of 'test_cmp <empty> <out>'

[git] / git-gui / .gitattributes

*           whitespace=indent-with-non-tab,trailing-space,space-before-tab,tabwidth=4
*           encoding=US-ASCII
git-gui.sh  encoding=UTF-8
/po/*.po    encoding=UTF-8
/GIT-VERSION-GEN eol=lf