t0027: make commit_chk_wrnNNO() reliable

t0027: make commit_chk_wrnNNO() reliable

When the content of a commited file is unchanged and the attributes
are changed, Git may not detect that the next commit must treat the
file as changed.  This happens when lstat() doesn't detect a change,
since neither inode, mtime nor size are changed.

Add a single "Z" character to change the file size and content.
When the files are compared later in checkout_files(), the "Z" is
removed before the comparison.

Signed-off-by: Torsten Bögershausen <redacted>
Signed-off-by: Junio C Hamano <redacted>