Provide an image with default Vims (including Neovim)

Fixes Vimjas#27.

Dockerfile.default

@@ -0,0 +1,20 @@
+# A set of default Vims, including Neovim.
+FROM testbed/vim
+
+# Currently tested versions:
+#  - v7.3.429 (Ubuntu Precise, 12.04LTS; same as on Travis currently)
+#  - v7.4.052 (Ubuntu Trusty, 14.04LTS)
+#  - v7.4.1689 (Ubuntu Xenial, 16.04LTS)
+#  - v8.0.8069 (Updated Vim 8, https://groups.google.com/forum/#!topic/vim_dev/ro_FpeXgc24)
+RUN install_vim -tag v7.3.429 -name vim73 -py -build \
+                -tag v7.4.052 -name vim74-trusty -build \
+                -tag v7.4.1689 -name vim74-xenial -build \
+                -tag v8.0.0069 -name vim8069 -build \
+                -tag neovim:v0.1.7 -py2 -py3 -build \
+                -tag neovim:v0.2.0 -py2 -py3 -build
+
+ENV _UPDATE=2017-05-02
+
+# Git master in a separate layer, since the above is meant to be stable.
+RUN install_vim -tag master -py3 -build \
+                -tag neovim:master -py2 -py3 -build

Makefile

@@ -1,12 +1,19 @@
 .PHONY: build push test
 
+DOCKER_REPO_BASE:=testbed/vim
+DOCKER_REPO_VIMS_DEFAULT:=testbed/vim-default
+
 TAG:=4
 
 build:
-	docker build -t testbed/vim:$(TAG) .
-
+	docker build -t $(DOCKER_REPO_BASE):$(TAG) .
 push:
-	docker push testbed/vim:$(TAG)
+	docker push $(DOCKER_REPO_BASE):$(TAG)
+
+build_default:
+	docker build -f Dockerfile.default -t $(DOCKER_REPO_VIMS_DEFAULT) .
+push_default:
+	docker push $(DOCKER_REPO_VIMS_DEFAULT)
 
 # test: build the base image and example image on top, running tests therein.
 DOCKER_BASE_IMAGE:=vim-testbed-base