├── .travis.yml
├── README.md
├── LICENSE
└── docker-rebase.go


/.travis.yml:
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 1 | language: go
 2 | go:
 3 |   - 1.2.1
 4 |   - tip
 5 | notifications:
 6 |   # See http://about.travis-ci.org/docs/user/build-configuration/ to learn more
 7 |   # about configuring notification recipients and more.
 8 |   email:
 9 |     recipients:
10 |       - coda.hale@gmail.com
11 | 


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/README.md:
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 1 | docker-rebase
 2 | =============
 3 | 
 4 | [![Build Status](https://travis-ci.org/codahale/docker-rebase.png?branch=master)](https://travis-ci.org/codahale/docker-rebase)
 5 | 
 6 | `docker-rebase` is used to "rebase" a Docker image against an base image. The
 7 | resulting image contains only those layers which are unique to the downstream
 8 | image:
 9 | 
10 | ```
11 | docker save base > base.tar
12 | docker save app | docker-rebase base.tar > app.tar
13 | ```
14 | 
15 | To install, run `go get -u github.com/codahale/docker-rebase`.
16 | 
17 | For documentation, check [godoc](http://godoc.org/github.com/codahale/docker-rebase).
18 | 


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/LICENSE:
--------------------------------------------------------------------------------
 1 | The MIT License (MIT)
 2 | 
 3 | Copyright (c) 2014 Coda Hale
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in
13 | all copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 | THE SOFTWARE.
22 | 


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/docker-rebase.go:
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 1 | // Command docker-rebase is used to "rebase" a Docker image against an base
 2 | // image. The resulting image contains only those layers which are unique to the
 3 | // downstream image.
 4 | //
 5 | // Example
 6 | //
 7 | //     docker save base > base.tar
 8 | //     docker save app | docker-rebase base.tar > app.tar
 9 | package main
10 | 
11 | import (
12 | 	"archive/tar"
13 | 	"io"
14 | 	"log"
15 | 	"os"
16 | )
17 | 
18 | func main() {
19 | 	if len(os.Args) < 2 {
20 | 		log.Fatal("no base image specified")
21 | 	}
22 | 
23 | 	excluded, err := ls(os.Args[1])
24 | 	if err != nil {
25 | 		log.Panic(err)
26 | 	}
27 | 
28 | 	if err := rebase(os.Stdin, os.Stdout, excluded); err != nil {
29 | 		log.Panic(err)
30 | 	}
31 | }
32 | 
33 | func rebase(in io.Reader, out io.Writer, excluded map[string]bool) error {
34 | 	r := tar.NewReader(in)
35 | 
36 | 	w := tar.NewWriter(out)
37 | 	defer w.Close()
38 | 
39 | 	for {
40 | 		h, err := r.Next()
41 | 		if err == io.EOF {
42 | 			break
43 | 		} else if err != nil {
44 | 			return err
45 | 		}
46 | 
47 | 		if !excluded[h.Name] {
48 | 			if err := w.WriteHeader(h); err != nil {
49 | 				return err
50 | 			}
51 | 
52 | 			if _, err := io.Copy(w, r); err != nil {
53 | 				return err
54 | 			}
55 | 		}
56 | 	}
57 | 
58 | 	return nil
59 | }
60 | 
61 | func ls(path string) (map[string]bool, error) {
62 | 	f, err := os.Open(path)
63 | 	if err != nil {
64 | 		return nil, err
65 | 	}
66 | 	defer f.Close()
67 | 
68 | 	files := make(map[string]bool)
69 | 	r := tar.NewReader(f)
70 | 	for {
71 | 		h, err := r.Next()
72 | 		if err == io.EOF {
73 | 			break
74 | 		} else if err != nil {
75 | 			return nil, err
76 | 		}
77 | 
78 | 		files[h.Name] = true
79 | 	}
80 | 
81 | 	// don't exclude the metadata
82 | 	delete(files, "./")
83 | 	delete(files, "repositories")
84 | 
85 | 	return files, nil
86 | }
87 | 


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