Multi-period (tar.gz) file extensions fix for extract_artifact!

[florentdupont]

Archives with multi-period extensions (like tar.gz for example) are not matched correctly by the extract_artifact! method.
The problem with the actual implementation is that ::File.extname() for a multi-period filename extension doesn't extract all the part but only the last unique extension after the last ..
For instance : foo.tar.gz gets an extension .gz instead of .tar.gz.

The use of an heuristic is necessary to guess the real extension. This heuristic is done inside the new extname() function.

For this correction, this function will return :

extname("test.rb")         #=> ".rb"
extname("a/b/d/test.rb")   #=> ".rb"
extname("foo.")            #=> ""
extname("test")            #=> ""
extname(".profile")        #=> ""
extname(".profile.sh")     #=> ".sh"
extname("myfile.tar.gz")   #=> ".tar.gz"
extname("my.file.tar.gz")  #=> ".tar.gz"
extname("tar.gz")          #=> ".gz"

[kainosnoema]

Amazing timing, I just hit this one as well. Looks like it was broken in 35eb0ab.

[colin-harms]

This is still an issue. As a result of this, the nexus-cookbook doesn't converge.
The nexus archive is: nexus-2.11.1-01-bundle.tar.gz