ptardiff is a small program that diffs an extracted archive against an unextracted one, using the perl module Archive::Tar.
This effectively lets you view changes made to an archives contents.
Provide the progam with an ARCHIVE_FILE and it will look up all the files with in the archive, scan the current working directory for a file with the name and diff it against the contents of the archive.
ptardiff ARCHIVE_FILE ptardiff -h
$ tar -xzf Acme-Buffy-1.3.tar.gz $ vi Acme-Buffy-1.3/README [...] $ ptardiff Acme-Buffy-1.3.tar.gz > README.patch
h Prints this help message