Added docker-build (formerly github.com/shykes/changer) as a contrib script

contrib/docker-build/README

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+# docker-build: build your software with docker
+
+## Description
+
+docker-build is a script to build docker images from source. It will be deprecated once the 'build' feature is incorporated into docker itself (See https://github.com/dotcloud/docker/issues/278)
+
+Author: Solomon Hykes <solomon@dotcloud.com>
+
+
+## Install
+
+docker-builder requires:
+
+1) A reasonably recent Python setup (tested on 2.7.2).
+
+2) A running docker daemon at version 0.1.4 or more recent (http://www.docker.io/gettingstarted)
+
+
+## Usage
+
+First create a valid Changefile, which defines a sequence of changes to apply to a base image.
+
+    $ cat Changefile
+    # Start build from a know base image
+    from	base:ubuntu-12.10
+    # Update ubuntu sources
+    run	echo 'deb http://archive.ubuntu.com/ubuntu quantal main universe multiverse' > /etc/apt/sources.list
+    run	apt-get update
+    # Install system packages
+    run	DEBIAN_FRONTEND=noninteractive apt-get install -y -q git
+    run DEBIAN_FRONTEND=noninteractive apt-get install -y -q curl
+    run DEBIAN_FRONTEND=noninteractive apt-get install -y -q golang
+    # Insert files from the host (./myscript must be present in the current directory)
+    copy	myscript /usr/local/bin/myscript
+
+
+Run docker-build, and pass the contents of your Changefile as standard input.
+
+    $ IMG=$(./docker-build < Changefile)
+
+This will take a while: for each line of the changefile, docker-build will:
+
+1. Create a new container to execute the given command or insert the given file
+2. Wait for the container to complete execution
+3. Commit the resulting changes as a new image
+4. Use the resulting image as the input of the next step
+
+
+If all the steps succeed, the result will be an image containing the combined results of each build step.
+You can trace back those build steps by inspecting the image's history:
+
+    $ docker history $IMG
+    ID                  CREATED             CREATED BY
+    1e9e2045de86        A few seconds ago   /bin/sh -c cat > /usr/local/bin/myscript; chmod +x /usr/local/bin/git
+    77db140aa62a        A few seconds ago   /bin/sh -c DEBIAN_FRONTEND=noninteractive apt-get install -y -q golang
+    77db140aa62a        A few seconds ago   /bin/sh -c DEBIAN_FRONTEND=noninteractive apt-get install -y -q curl
+    77db140aa62a        A few seconds ago   /bin/sh -c DEBIAN_FRONTEND=noninteractive apt-get install -y -q git 
+    83e85d155451        A few seconds ago   /bin/sh -c apt-get update
+    bfd53b36d9d3        A few seconds ago   /bin/sh -c echo 'deb http://archive.ubuntu.com/ubuntu quantal main universe multiverse' > /etc/apt/sources.list
+    base		2 weeks ago         /bin/bash
+    27cf78414709        2 weeks ago
+
+
+Note that your build started from 'base', as instructed by your Changefile. But that base image itself seems to have been built in 2 steps - hence the extra step in the history.
+
+
+You can use this build technique to create any image you want: a database, a web application, or anything else that can be build by a sequence of unix commands - in other words, anything else.
+

contrib/docker-build/docker-build

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+#!/usr/bin/env python
+
+# docker-build is a script to build docker images from source.
+# It will be deprecated once the 'build' feature is incorporated into docker itself.
+# (See https://github.com/dotcloud/docker/issues/278)
+#
+# Author: Solomon Hykes <solomon@dotcloud.com>
+
+
+
+# First create a valid Changefile, which defines a sequence of changes to apply to a base image.
+# 
+#     $ cat Changefile
+#     # Start build from a know base image
+#     from	base:ubuntu-12.10
+#     # Update ubuntu sources
+#     run	echo 'deb http://archive.ubuntu.com/ubuntu quantal main universe multiverse' > /etc/apt/sources.list
+#     run	apt-get update
+#     # Install system packages
+#     run	DEBIAN_FRONTEND=noninteractive apt-get install -y -q git
+#     run DEBIAN_FRONTEND=noninteractive apt-get install -y -q curl
+#     run DEBIAN_FRONTEND=noninteractive apt-get install -y -q golang
+#     # Insert files from the host (./myscript must be present in the current directory)
+#     copy	myscript /usr/local/bin/myscript
+# 
+# 
+# Run docker-build, and pass the contents of your Changefile as standard input.
+# 
+#     $ IMG=$(./docker-build < Changefile)
+# 
+# This will take a while: for each line of the changefile, docker-build will:
+# 
+# 1. Create a new container to execute the given command or insert the given file
+# 2. Wait for the container to complete execution
+# 3. Commit the resulting changes as a new image
+# 4. Use the resulting image as the input of the next step
+
+
+import sys
+import subprocess
+import json
+import hashlib
+
+def docker(args, stdin=None):
+	print "# docker " + " ".join(args)
+	p = subprocess.Popen(["docker"] + list(args), stdin=stdin, stdout=subprocess.PIPE)
+	return p.stdout
+
+def image_exists(img):
+	return docker(["inspect", img]).read().strip() != ""
+
+def run_and_commit(img_in, cmd, stdin=None):
+	run_id = docker(["run"] + (["-i", "-a", "stdin"] if stdin else ["-d"]) + [img_in, "/bin/sh", "-c", cmd], stdin=stdin).read().rstrip()
+	print "---> Waiting for " + run_id
+	result=int(docker(["wait", run_id]).read().rstrip())
+	if result != 0:
+		print "!!! '{}' return non-zero exit code '{}'. Aborting.".format(cmd, result)
+		sys.exit(1)
+	return docker(["commit", run_id]).read().rstrip()
+
+def insert(base, src, dst):
+	print "COPY {} to {} in {}".format(src, dst, base)
+	if dst == "":
+		raise Exception("Missing destination path")
+	stdin = file(src)
+	stdin.seek(0)
+	return run_and_commit(base, "cat > {0}; chmod +x {0}".format(dst), stdin=stdin)
+	
+
+def main():
+	base=""
+	steps = []
+	try:
+		for line in sys.stdin.readlines():
+			line = line.strip()
+			# Skip comments and empty lines
+			if line == "" or line[0] == "#":
+				continue
+			op, param = line.split("	", 1)
+			if op == "from":
+				print "FROM " + param
+				base = param
+				steps.append(base)
+			elif op == "run":
+				print "RUN " + param
+				result = run_and_commit(base, param)
+				steps.append(result)
+				base = result
+				print "===> " + base
+			elif op == "copy":
+				src, dst = param.split("	", 1)
+				result = insert(base, src, dst)
+				steps.append(result)
+				base = result
+				print "===> " + base
+			else:
+				print "Skipping uknown op " + op
+	except:
+		docker(["rmi"] + steps)
+		raise
+	print base
+
+if __name__ == "__main__":
+	main()

contrib/docker-build/example.changefile

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+# Start build from a know base image
+from	base:ubuntu-12.10
+# Update ubuntu sources
+run	echo 'deb http://archive.ubuntu.com/ubuntu quantal main universe multiverse' > /etc/apt/sources.list
+run	apt-get update
+# Install system packages
+run	DEBIAN_FRONTEND=noninteractive apt-get install -y -q git
+run DEBIAN_FRONTEND=noninteractive apt-get install -y -q curl
+run DEBIAN_FRONTEND=noninteractive apt-get install -y -q golang
+# Insert files from the host (./myscript must be present in the current directory)
+copy	myscript /usr/local/bin/myscript