FS2: Use Cases and Reasons for Redesigning
Notes from Ben/Brane/Julian/Stefan on 2012-10-25
UCs & Reasons
- svnsync: locks / rev-props
- applicable to incremental backups
- GUI updating of locks / rev-props
- Inhume "externals"
- Mergeinfo / other unversioned data
- Forward history tracing
- Audit trail: rev-props / locks? / access control
- Optimizable for (e.g.) size of data representation (Representation-agnistic API)
- Abstracted from DB (SQL, distubuted, LevelDB, ...)
"Versioned history" means
"Audit trail" means
Reversible / time-safe (except for Obliterate which deliberately breaks this property)
Not necessarily reversible / time-safe. It can be OK to just store a description of / metadata about each change that happened.
History: for all time
History: time span can be dynamically limited (FIFO)
Details of the UCs & Reasons
Details with respect to the semantic properties of the whole-system design and of the file-system design.
svnsync: locks / rev-props
GUI updating of locks / rev-props
Replace "externals" with:
- FS-level symlinks/"reparse points"
- cross-repository branch/merge (e.g., proper vendor branches)
- foreign-repository branch import (e.g., track git branch in svn)
A node kind (in repository) alonside 'file' and 'dir', that:
- appears as a named child of a directory (in the same way as 'file' and 'dir' nodes do)
- points to another node, by specifying 'node-id.branch-id[.txn-id?]'
- optionally specifies a revision number
The client / WC:
- doesn't see symlinks, but just sees a single versioned tree of files and dirs
- (therefore) recurses into them and behaves exactly as on a 'normal' WC
- knows when a node is "pinned" to a specified revision number and SHOULD block modifications and commits in such a subtree
Compared with (same-repos) 'externals':
- Ensures consistent behaviour of the client
- Allows the client to block modifications and commits in a "pinned" external
- Implications for merging, especially w.r.t. cross-branch externals?
Mergeinfo / other unversioned data
Forward history tracing
Audit trail: rev-props / locks? / access control
Optimizable for (e.g.) size of data representation (Representation-agnistic API)
Abstracted from DB (SQL, distubuted, LevelDB, ...)