gitty.pl -- Single-file GIT like version system

This library provides a first implementation of a lightweight versioned file store with dynamic meta-data. The store is partly modelled after GIT. Like GIT, it uses a content-based store. In fact, the stored objects are compatible with GIT. Unlike GIT though, there are no trees. Each entry (file) has its own history. Each commit is associated with a dict that can carry aribitrary meta-data. The following fields are reserved for gitties bookkeeping:

name:Name: Name of the entry (file)
time:TimeStamp: Float representing when the object was added to the store
data:Hash: Object hash of the contents
previous:Hash: Hash of the previous commit.

The key commit is reserved and returned as part of the meta-data of the newly created (gitty_create/5) or updated object (gitty_update/5).

gitty_open(+Store, +Options) is det

Open a gitty store according to Options. Defined options are:

driver(+Driver): Backend driver to use. One of files or bdb. When omitted and the store exists, the current store is examined. If the store does not exist, the default is files.

gitty_driver(+Store, -Driver)

Get the current gitty driver

gitty_close(+Store) is det

Close access to the Store.

gitty_file(+Store, ?Head, ?Hash) is nondet

gitty_file(+Store, ?Head, ?Ext, ?Hash) is nondet

True when Hash is an entry in the gitty Store and Head is the HEAD revision.

gitty_create(+Store, +Name, +Data, +Meta, -Commit) is det

Create a new object Name from Data and meta information.

Arguments:

Commit

- is a dit describing the new Commit

gitty_update(+Store, +Name, +Data, +Meta, -Commit) is det

Update document Name using Data and the given meta information

gitty_data(+Store, +NameOrHash, -Data, -Meta) is semidet

Get the data in object Name and its meta-data

gitty_commit(+Store, +NameOrHash, -Meta) is semidet

True if Meta holds the commit data of NameOrHash. A key commit is added to the meta-data to specify the commit hash.

gitty_history(+Store, +NameOrHash, -History, +Options) is det

History is a dict holding a key history with a list of dicts representating the history of Name in Store. The toplevel dict also contains skipped, indicating the number of skipped items from the HEAD. Options:

depth(+Depth): Number of entries in the history. If not present, defaults to 5.
includes(+HASH): Ensure Hash is included in the history. This means that the history includes the entry with HASH an (depth+1)//2 entries after the requested HASH.

gitty_fsck(+Store) is det

Check the integrity of store.

fsck_object(+Store, +Hash) is semidet

Test the integrity of object Hash in Store.

gitty_save(+Store, +Data, +Type, -Hash) is det

gitty_load(+Store, +Hash, -Data, -Type) is det

Low level objects store. These predicate allows for using the store as an arbitrary content store.

Arguments:

`Data`	- is a string
`Type`	- is an atom denoting the object type.

gitty_hash(+Store, ?Hash) is nondet

True when Hash is an object in the store.

delete_object(+Store, +Hash)

Delete an existing object

gitty_reserved_meta(?Key) is nondet

True when Key is a gitty reserved key for the commit meta-data

is_gitty_hash(@Term) is semidet

True if Term is a possible gitty (SHA1) hash

delete_head(+Store, +Head) is det

Delete Head from the administration. Used if the head is inconsistent.

set_head(+Store, +File, +Head) is det

gitty_diff(+Store, ?Hash1, +FileOrHash2OrData, -Dict) is det

True if Dict representeds the changes in Hash1 to FileOrHash2. If Hash1 is unbound, it is unified with the previous of FileOrHash2. Returns _{initial:true} if Hash1 is unbound and FileOrHash2 is the initial commit. Dict contains:

from:Meta1
to:Meta2: Meta-data for the two diffed versions
data:UDiff: String holding unified diff representation of changes to the data. Only present of data has changed
tags:_121926{added:AddedTags, deleted:DeletedTags}: If tags have changed, the added and deleted ones.

Arguments:

FileOrHash2OrData - is a file name, hash or a term data(String) to compare a given string with a gitty version.

data_diff(+Data1, +Data2, -UDiff) is det

Diff two data strings line-by-line. UDiff is a list of terms of the form below, where L1 and L2 provide the starting line in Data1 and Data2 and S1 and S2 provide the number of affected lines.

udiff(L1,S1,L2,S2,Diff)

Diff is a list holding

+ Line: Line was added to Data1 to get Data2
- Line: Line was deleted from Data1 to get Data2
Line1 - Line2: Line was replaced
=(Line): Line is identical (context line).

udiff_string(+UDiff, -String) is det

True when String is the string representation of UDiff.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

gitty_load(Arg1, Arg2, Arg3, Arg4)
gitty_file(Arg1, Arg2, Arg3, Arg4)