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by mbp at sourcefrog
import all docs from arch |
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* Write-once store of files identified by globally-unique names |
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(e.g. hashes or UUIDs). |
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Simplest option is to just dump them in a directory. |
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Optionally do delta-compression between similar/related files; or |
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build this on top of deltas. |
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* Tree manifests/inventories which say which files should be assembled at |
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particular points to build a tree. These too can be stored indexed |
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by hash. |
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- Reconstruct a revision by pulling out the manifest and then all |
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the individual files. |
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- Manipulate working copy of inventory by add/mv/remove/commands. |
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* Retrieve deltas |
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- Calculate diffs between two file versions, just by getting them |
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from the store. |
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- Retrieve deltas between any two revisions: requires looking for |
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changes to the structure of the tree, and then text changes for |
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anything inside it. |
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- Deltas may be either stored or calculated on demand. They can be |
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put in the store just indexed by the from and to manifest id. |
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- Calculate diff between a previous revision and the working copy. |
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* Commit and retrieve revisions |
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- Revisions hold metadata (date, committer, comment, optional |
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parents, merged patches), and a pointer to the inventory. |
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- Stored in a write-once store. |
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* Branch holds a linear history of revisions. |
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- This is mostly redundant; we could just remember the current base |
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revision and walk backwards from there. But it still seems |
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possibly useful to hold; we can check that the two are always |
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consistent. |
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(This suggests that we actually *could* do ``switch`` if we |
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really wanted to, by replacing the revision history and head |
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revision. But I don't think it's a good idea.) |
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- Can add a new revision to the end. |
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- By indexing into this can translate between 0-based revision |
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numbers and revision ids. |
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- By walking through and looking at revision dates can find |
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revisions in a particular date range. |
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* Calculations on branch histories: |
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- Find if one branch is a prefix of another. |
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- Find the latest common ancestor of another. |
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* Three-way merge between revisions |
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- Resolve shape of directory |
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- Then resolve textual conflicts |
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* Pull/push changes when they perfectly match |
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- Possible when the destination is a prefix of the source |
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- Just move all revisions, manifests and texts across, and |
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* Merge all changes from one branch into another |
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* Signatures applied to revisions |
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- There is a separable module for checking a signature: this is |
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passed the claimed author, changeset, date. This needs to fetch |
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an appropriate key, decide if it is trusted to correspond to that |
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author, is not revoked, etc. |
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- If it is unknown, untrusted, revoked, etc, that is reported. |
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Depending on a paranoia level it may cause the operation to |
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abort. |
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