├── .dockerignore
├── .gitignore
├── apk-motd
├── Dockerfile
└── flatten.py


/.dockerignore:
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1 | .gitignore


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/.gitignore:
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1 | /out
2 | 


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/apk-motd:
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1 | Welcome to Alpine!
2 | 
3 | You can install packages with: apk add <package>
4 | 
5 | You may change this message by editing /etc/motd.
6 | 
7 | 


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/Dockerfile:
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1 | FROM --platform=linux/386 docker.io/library/alpine:3.19.0 AS ish-alpine
2 | 
3 | FROM ish-alpine
4 | LABEL ish.export=appstore-apk.tar.gz
5 | RUN mkdir /ish && touch /ish/version
6 | RUN echo 31900 > /ish/apk-version
7 | COPY apk-motd /etc/motd
8 | 


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/flatten.py:
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 1 | #!/usr/bin/env python3
 2 | import json
 3 | import os
 4 | import sys
 5 | import tarfile
 6 | 
 7 | WHITEOUT = '.wh.'
 8 | WHITEOUT_OPAQUE = '.wh..wh..opq'
 9 | 
10 | def flatten(image, output):
11 |     manifest = json.load(image.extractfile('manifest.json'))
12 |     assert len(manifest) == 1
13 |     manifest = manifest[0]
14 | 
15 |     entries = {}
16 |     layers = [tarfile.open(fileobj=image.extractfile(layer)) for layer in manifest['Layers']]
17 |     for layer in layers:
18 |         real_members = []
19 |         # process whiteout files
20 |         for info in layer.getmembers():
21 |             info.name = './' + info.name
22 |             dirname, sep, basename = info.name.rpartition('/')
23 | 
24 |             if basename == WHITEOUT_OPAQUE:
25 |                 for key in entries.keys():
26 |                     if key.startswith(dirname+sep):
27 |                         del entries[key]
28 |             elif basename.startswith(WHITEOUT):
29 |                 del entries[dirname+sep+basename[len(WHITEOUT):]]
30 |             else:
31 |                 real_members.append(info)
32 |                 continue
33 | 
34 |         # real files
35 |         for info in real_members:
36 |             entries[info.name] = layer, info
37 | 
38 |     # need a root entry
39 |     if './' not in entries:
40 |         info = tarfile.TarInfo('./')
41 |         info.type = tarfile.DIRTYPE
42 |         info.mode = 0o755
43 |         entries[info.name] = None, info
44 | 
45 |     for layer, info in entries.values():
46 |         fileobj = layer.extractfile(info) if info.isfile() else None
47 |         info.mtime = 0 # make reproducible
48 |         output.addfile(info, fileobj)
49 | 
50 |     for layer in layers:
51 |         layer.close()
52 | 
53 | with tarfile.open(sys.argv[1]) as image:
54 |     with tarfile.open(fileobj=sys.stdout.buffer, mode='w|') as output:
55 |         flatten(image, output)
56 | 


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