In preparation for removing the common package, the tarsum utilities are being
moved to the more relevant digest package. This functionality will probably go
away in the future, but it's maintained here for the time being.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit adds regular expression definitions for several string identifiers
used througout the registry. The repository name regex supports up to five path
path components and restricts repeated periods, dashes and underscores. The tag
regex simply validates the length of the tag and that printable characters are
required.
Though we define a new package common, these definition should land in docker
core.
