Joseph Martinot-Lagarde writes:
One remark about this : .tar.gz files are the exception rather than the rule, and AFAIK maybe the only one ?
Not really. stem.ext -> stem.ext.zzz where zzz is a compression extension is a pretty common naming convention. For me ext == 'tar' is by far the most common case (74%), 'tis true, but 'patch' (10%), 'txt' (6%), 'tab', 'gml', 'xml', 'svg', 'pdf', 'ps', ' dvi', 'diff', 'pdb', 'cpp', 'el', and 'data' also exist somewhere under $HOME. I'll bet others show up if I search /usr, /var, and /opt.