Vendor in latest github.com/projectatomic/buildah

This adds support for Dockerfile.in and fixes some limits
issues on docker build

Also adds support for podman build to read Dockerfile from stdin.

cat Dockerfile | podman build -f - .

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Closes: #1209
Approved by: mheon
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f