Make makefile a bit more powerful.

Dockerfile.repro

@@ -1,8 +1,10 @@
-FROM ultisnips
+ARG BASE_IMAGE
+
+FROM ultisnips:${BASE_IMAGE}
 
 RUN curl -fLo ~/.vim/autoload/plug.vim --create-dirs \
     https://raw.githubusercontent.com/junegunn/vim-plug/master/plug.vim
 
-ADD doc/minimal_vimrc.vim /root/.vimrc
+ADD scripts/docker_vimrc.vim /root/.vimrc
 
 RUN vim -c 'PlugInstall | qa'

Makefile

@@ -0,0 +1,24 @@
+
+# Test images as run on CI.
+image_vim_74_py2:
+	docker build -t ultisnips:$@ --build-arg PYTHON_IMAGE=2.7-stretch --build-arg VIM_VERSION=7.4 .
+image_vim_80_py2:
+	docker build -t ultisnips:$@ --build-arg PYTHON_IMAGE=2.7-stretch --build-arg VIM_VERSION=8.0 .
+image_vim_git_py2:
+	docker build -t ultisnips:$@ --build-arg PYTHON_IMAGE=2.7-stretch --build-arg VIM_VERSION=git .
+image_vim_74_py3:
+	docker build -t ultisnips:$@ --build-arg PYTHON_IMAGE=3.6-stretch --build-arg VIM_VERSION=7.4 .
+image_vim_80_py3:
+	docker build -t ultisnips:$@ --build-arg PYTHON_IMAGE=3.6-stretch --build-arg VIM_VERSION=8.0 .
+image_vim_git_py3:
+	docker build -t ultisnips:$@ --build-arg PYTHON_IMAGE=3.6-stretch --build-arg VIM_VERSION=git .
+
+image_repro: image_vim_80_py3
+	docker build -t ultisnips:repro --build-arg BASE_IMAGE=$< -f Dockerfile.repro .
+
+# A reproduction image that drops you into a naked environment,
+# with a Vim having UltiSnips and vim-snippets configured. See
+# scripts/docker_vimrc.vim for the full vimrc. Need to run `make
+# image_repro` before this will work.
+repro:
+	docker run -it -v $(pwd):/src/UltiSnips ultisnips:repro /bin/bash

scripts/docker_vimrc.vim

@@ -1,6 +1,6 @@
 call plug#begin('~/.vim/plugged')
 
-Plug 'SirVer/ultisnips'
+Plug '/src/UltiSnips'
 Plug 'honza/vim-snippets'
 
 let g:UltiSnipsExpandTrigger="<tab>"