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Excerpts from Brownell, Jonathan C (Corvallis)'s message of 2014-08-15 08:11:18 -0700:
> The current DIB element support for downloading tarballs via "source-repository" allows an entry in the following form:
> 
> <name> tar <targetdir> <url>
> 
> Today, this feature is currently used only by the mysql DIB element. You can see how it's used here:
> https://github.com/openstack/tripleo-image-elements/blob/master/elements/mysql/source-repository-mysql
> 
> However, the underlying diskimage-builder implementation of tarball handling is rather odd and inflexible. After downloading the file (or retrieving from cache) and unpacking into a tmp directory, it performs:
> 
> mv $tmp/*/* $targetdir
> 
> This does work as long as the tarball follows a structure where all its files/directories are contained within a single directory, but it fails if the tarball contains no subdirectories. (Even worse is when it contains some files and some subdirectories, in which case the files are lost and the contents of all subdirs get lumped together in the output folder.)
> 
> Since this tarball support is only used today by the mysql DIB element, I would love to fix this in both diskimage-builder and tripleo-image-element by changing to simply:
> 
> mv $tmp/* $targetdir
> 
> And then manually tweaking the directory structure of $targetdir from a new install.d script in the mysql element to restore the desired layout.
> 
> However, it's important to note that this will break backwards compatibility if tarball support is used in its current fashion by users with private DIB elements.
> 
> Personally, I consider the current behavior so egregious that it really needs to be fixed across the board rather than preserving backwards compatibility.
> 
> Do others agree? If not, do you have suggestions as to how to improve this mechanism cleanly without sacrificing backwards compatibility?
> 

How about we make a glob to use, so like this:

mysql tar /usr/local/mysql http://someplace/mysql.tar.gz mysql-5.*

That would result in

    mv $tmp/mysql-5.*/* $targetdir

And then we would warn that assuming the glob will be '*' is deprecated,
to be changed in a later release.

Users who want your proposed behavior would use . until the default
changes. That would result in

    mv $tmp/./* $targetdir