v1.7.3

• imagebuildah: don't leak image structs
• Add Dockerfiles for buildahimages
• Bump to Replace golang 1.10 with 1.12
• add --dns* flags to buildah bud
• Add hack/build_speed.sh test speeds on building container images
• Create buildahimage Dockerfile for Quay
• rename 'is' to 'expect_output'
• squash.bats: test squashing in multi-layered builds
• bud.bats: test COPY --from in a Dockerfile while using the cache
• commit: make target image names optional
• Fix bud-args to allow comma separation
• oops, missed some tests in commit.bats
• new helper: expect_line_count
• New tests for #1467 (string slices in cmdline opts)
• Workarounds for dealing with travis; review feedback
• BATS tests - extensive but minor cleanup
• imagebuildah: defer pulling images for COPY --from
• imagebuildah: centralize COMMIT and image ID output
• Travis: do not use traviswait
• imagebuildah: only initialize imagebuilder configuration once per stage
• Make cleaner error on Dockerfile build errors
• unshare: move to pkg/
• unshare: move some code from cmd/buildah/unshare
• Fix handling of Slices versus Arrays
• imagebuildah: reorganize stage and per-stage logic
• imagebuildah: add empty layers for instructions
• Add missing step in installing into Ubuntu
• fix bug in .dockerignore support
• imagebuildah: deduplicate prepended "FROM" instructions
• Touch up intro
• commit: set created-by to the shell if it isn't set
• commit: check that we always set a "created-by"
• docs/buildah.md: add "containers-" prefixes under "SEE ALSO"
• Bump back to 1.8-dev