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move git comparison to related work

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it should be pulled out of the branch before we go for merging
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Valentin Gagarin 2022-04-28 10:16:27 +02:00
parent a145007a57
commit e5e48593c8
2 changed files with 24 additions and 23 deletions
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23
doc/manual/src/architecture/store/objects.md
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@ -31,29 +31,6 @@ In particular, every file system object falls into these three cases:
A bare file or symlink as the "root" file system object is allowed. A bare file or symlink as the "root" file system object is allowed.
### Comparison with Git
This is close to Git's model, but with one crucial difference:
Git puts the "permission" info within the directory map's values instead of making it part of the file (blob, in it's parlance) object.
data GitObject
= Blob ByteString
| Tree (Map FileName (Persission, FSO))
data Persission
= Directory -- IFF paired with tree
-- Iff paired with blob, one of:
| RegFile
| ExecutableFile
| Symlink
So long as the root object is a directory, the representations are isomorphic.
There is no "wiggle room" the git way since whenever the permission info wouldn't matter (e.g. the child object being mapped to is a directory), the permission info must be a sentinel value.
However, if the root object is a blob, there is loss of fidelity.
Since the permission info is used to distinguish executable files, non-executable files, and symlinks, but there isn't a "parent" directory of the root to contain that info, these 3 cases cannot be distinguished.
Git's model matches Unix tradition, but Nix's model is more natural.
## References ## References

24
doc/manual/src/architecture/store/related-work.md
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@ -25,6 +25,30 @@ Do we have open terms?
Do we hve thunks vs expressions distinction? Do we hve thunks vs expressions distinction?
c.f. John Shutt's modern fexprs, when the syntax can "leak". c.f. John Shutt's modern fexprs, when the syntax can "leak".
## Comparison with Git file system model
This is close to Git's model, but with one crucial difference:
Git puts the "permission" info within the directory map's values instead of making it part of the file (blob, in it's parlance) object.
data GitObject
= Blob ByteString
| Tree (Map FileName (Persission, FSO))
data Persission
= Directory -- IFF paired with tree
-- Iff paired with blob, one of:
| RegFile
| ExecutableFile
| Symlink
So long as the root object is a directory, the representations are isomorphic.
There is no "wiggle room" the git way since whenever the permission info wouldn't matter (e.g. the child object being mapped to is a directory), the permission info must be a sentinel value.
However, if the root object is a blob, there is loss of fidelity.
Since the permission info is used to distinguish executable files, non-executable files, and symlinks, but there isn't a "parent" directory of the root to contain that info, these 3 cases cannot be distinguished.
Git's model matches Unix tradition, but Nix's model is more natural.
## Machine models ## Machine models
TODO TODO