https://github.com/noteed/try-bup

Docker image to play with Bup
https://github.com/noteed/try-bup

Last synced: about 2 months ago
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Docker image to play with Bup

• Host: GitHub
• URL: https://github.com/noteed/try-bup
• Owner: noteed
• Created: 2014-05-12T19:19:29.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2015-10-20T22:25:11.000Z (about 9 years ago)
• Last Synced: 2023-04-13T10:31:56.794Z (over 1 year ago)
• Language: Shell
• Size: 160 KB
• Stars: 0
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Exploring Bup

This is a Docker image to play with [Bup](https://github.com/bup/bup). The idea

is to

    > make run

in this repository to see how Bup compares to Git. See `RUN.md` for the output.

There also notes about Git.

## Notes

The command

    > echo hello | git hash-object --stdin -w

    ce013625030ba8dba906f756967f9e9ca394464a

creates the file (and nothing else) in the git object store:

    .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a

The result of these two commands is the same:

    > cat .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a | openssl zlib -d

    # Or, if your version of openssl doesn't have a zlib subcommand:

    > cat .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a | zlib-flate -uncompress

    > printf 'blob 6\x00hello\n'

Thus `git hash-object -w` can be replaced by

    > printf 'blob 6\x00hello\n' | sha1sum

    ce013625030ba8dba906f756967f9e9ca394464a

    # Not exactly...

    > printf 'blob 6\x00hello\n' | openssl zlib > .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a

but (using the original object):

    > cat .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a | openssl zlib -d | openssl zlib > a

    > printf 'blob 6\x00hello\n' | openssl zlib > b

    > diff a b

    > cat .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a > a

    > diff a b

    Binary files a and b differ

and

    > file a

    a: VAX COFF executable not stripped

    > file b

    b: data

The reason is that it seems Git and `openssl zlib` don't use the same

compression level (hence the two-byte headers are different).

    > printf 'blob 6\x00hello\n' | zlib-flate -compress > a

    > hexdump a

    0000000 9c78 ca4b 4fc9 3052 c863 cd48 c9c9 02e7

    0000010 1d00 04c5 0014

    0000015

    > hexdump .git/objects/ce/013625030ba8dba906f756967f9e9ca394464a

    0000000 0178 ca4b 4fc9 3052 c863 cd48 c9c9 02e7

    0000010 1d00 04c5 0014

    0000015