Commits on Oct 21, 2019

1. Allow content-addressable paths to have references …

   This adds a command 'nix make-content-addressable' that rewrites the
   specified store paths into content-addressable paths. The advantage of
   such paths is that 1) they can be imported without signatures; 2) they
   can enable deduplication in cases where derivation changes do not
   cause output changes (apart from store path hashes).
   
   For example,
   
     $ nix make-content-addressable -r nixpkgs.cowsay
     rewrote '/nix/store/g1g31ah55xdia1jdqabv1imf6mcw0nb1-glibc-2.25-49' to '/nix/store/48jfj7bg78a8n4f2nhg269rgw1936vj4-glibc-2.25-49'
     ...
     rewrote '/nix/store/qbi6rzpk0bxjw8lw6azn2mc7ynnn455q-cowsay-3.03+dfsg1-16' to '/nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16'
   
   We can then copy the resulting closure to another store without
   signatures:
   
     $ nix copy --trusted-public-keys '' ---to ~/my-nix /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16
   
   In order to support self-references in content-addressable paths,
   these paths are hashed "modulo" self-references, meaning that
   self-references are zeroed out during hashing. Somewhat annoyingly,
   this means that the NAR hash stored in the Nix database is no longer
   necessarily equal to the output of "nix hash-path"; for
   content-addressable paths, you need to pass the --modulo flag:
   
     $ nix path-info --json /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16  | jq -r .[].narHash
     sha256:0ri611gdilz2c9rsibqhsipbfs9vwcqvs811a52i2bnkhv7w9mgw
   
     $ nix hash-path --type sha256 --base32 /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16
     1ggznh07khq0hz6id09pqws3a8q9pn03ya3c03nwck1kwq8rclzs
   
     $ nix hash-path --type sha256 --base32 /nix/store/iq6g2x4q62xp7y7493bibx0qn5w7xz67-cowsay-3.03+dfsg1-16 --modulo iq6g2x4q62xp7y7493bibx0qn5w7xz67
     0ri611gdilz2c9rsibqhsipbfs9vwcqvs811a52i2bnkhv7w9mgw

   

   edolstra committed Oct 21, 2019
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   0abb3ad View commit details

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2. Fix build

   

   edolstra committed Oct 21, 2019
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   d77970f View commit details

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3. nix make-content-addressable: Add examples

   

   edolstra committed Oct 21, 2019
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   e687369 View commit details

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4. Mark content-addressable paths with references as experimental

   

   edolstra committed Oct 21, 2019
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   629b9b0 View commit details

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