We were leaking the temporary directory that we create in TarFilter,
because the "tmpDir, err := ioutil.TempDir()" call overrides the
tmpDir in the outer scope with a new locally scoped variable.
This means tmpDir is always "" when the cleanup function is called.
Also, we did not call the atExit() function if CmdStream had an
error early on.
On errors in CmdStream(),
There are a few changes:
* Callers can specify if they want recursive behaviour or not
* All file listings to tar are sent on stdin, to handle long lists better
* We can pass in a list of filenames which will be created as empty
files in the tarball
This is exactly what we want for the creation of layer tarballs given
a container fs, a set of files to add and a set of whiteout files to create.
into the container instead of copying them as a regular file.
* Builder: ADD uses tar/untar for copies instead of calling 'cp -ar'.
This is more consistent, reduces the number of dependencies, and
fixe #896.
As per FIXME, CmdStream could have deadlocked if a command printed
enough on stderr. This commit fixes that, but still keeps all of
the stderr output in memory.
