tarsum: name collision fix

If a tar were constructed with duplicate file names, then depending on
the order, it could result in same tarsum.

This does not break the existing checksums of correctly produced layers.

Signed-off-by: Vincent Batts <vbatts@redhat.com>
Something is fishy. That sort was removed. Must be a bad rebase. :-/
On Sep 16, 2014 6:35 PM, "unclejack" <notifications@github.com> wrote:

> In pkg/tarsum/tarsum.go:
>
> > @@ -7,7 +7,6 @@ import (
> >  	"encoding/hex"
> >  	"hash"
> >  	"io"
> > -	"sort"
>
> This is still needed:
>
> pkg/tarsum/tarsum.go:105: undefined: sort
>
> 105: sort.Strings(keys)
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/docker/docker/pull/7889/files#r17635072>.
>