**********************************************************************
Git objects
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.. contents:: Contents
   :local:


In the first place Git is a key-value storage system. The values stored are
called *objects*, there are four types (commits, trees, blobs and tags),
for each type pygit2 has a Python class::

    >>> # Get the last commit
    >>> head = repo.head

    >>> # Show commits and trees
    >>> commit
    <pygit2.Commit object at 0x7f9d2f3000b0>
    >>> commit.tree
    <pygit2.Tree object at 0x7f9d2f3000f0>

These four classes (``Commit``, ``Tree``, ``Blob`` and ``Tag``) inherit from
the ``Object`` base class, which provides shared behaviour. A Git object is
identified by a unique *object id*, which is a binary byte string; this is
often represented as an hexadecimal text string::

    >>> commit.oid
    b'x\xde\xb5W\x8d\x01<\xdb\xdf\x08o\xa1\xd1\xa3\xe7\xd9\x82\xe8\x88\x8f'
    >>> commit.hex
    '78deb5578d013cdbdf086fa1d1a3e7d982e8888f'

The API of pygit2 accepts both the raw object id and its hexadecimal
representation, the difference is done based on its type (a byte or a text
string).

Objects can not be modified once they have been created.

This is the common interface for all Git objects:

.. autoclass:: pygit2.Object
   :members: type, oid, hex, read_raw


Commits
-----------------

A commit is a snapshot of the working dir with meta informations like author,
committer and others.

.. autoclass:: pygit2.Commit
   :members: author, committer, message, message_encoding, tree, parents,
             commit_time, commit_time_offset
   :show-inheritance:


Signatures
.............

The author and committer attributes of commit objects are ``Signature``
objects::

    >>> commit.author
    <pygit2.Signature object at 0x7f75e9b1f5f8>

.. autoclass:: pygit2.Signature
   :members: name, email, time, offset


Creating commits
................

Commits can be created by calling the ``create_commit`` method of the
repository with the following parameters::

    >>> author = Signature('Alice Author', 'alice@authors.tld')
    >>> committer = Signature('Cecil Committer', 'cecil@committers.tld')
    >>> tree = repo.TreeBuilder().write()
    >>> repo.create_commit(
    ... 'refs/heads/master', # the name of the reference to update
    ... author, committer, 'one line commit message\n\ndetailed commit message',
    ... tree, # binary string representing the tree object ID
    ... [] # list of binary strings representing parents of the new commit
    ... )
    '#\xe4<u\xfe\xd6\x17\xa0\xe6\xa2\x8b\xb6\xdc35$\xcf-\x8b~'


Trees
-----------------

A tree is a sorted collection of tree entries. It is similar to a folder or
directory in a file system. Each entry points to another tree or a blob.  A
tree can be iterated, and partially implements the sequence and mapping
interfaces::

    >>> # Number of entries
    >>> tree = commit.tree
    >>> len(tree)
    6

    >>> # Iteration
    >>> for entry in tree:
    ...     print(entry.hex, entry.name)
    ...
    7151ca7cd3e59f3eab19c485cfbf3cb30928d7fa .gitignore
    c36f4cf1e38ec1bb9d9ad146ed572b89ecfc9f18 COPYING
    32b30b90b062f66957d6790c3c155c289c34424e README.md
    c87dae4094b3a6d10e08bc6c5ef1f55a7e448659 pygit2.c
    85a67270a49ef16cdd3d328f06a3e4b459f09b27 setup.py
    3d8985bbec338eb4d47c5b01b863ee89d044bd53 test

    >>> # Get an entry by name
    >>> entry = tree['pygit2.c']
    >>> entry
    <pygit2.TreeEntry object at 0xcc10f0>

    >>> # Get the object the entry points to
    >>> blob = repo[entry.oid]
    >>> blob
    <pygit2.Blob object at 0xcc12d0>

This is the interface of a tree entry::

    TreeEntry.name        -- name of the tree entry
    TreeEntry.oid         -- the id of the git object
    TreeEntry.hex         -- hexadecimal representation of the oid
    TreeEntry.filemode    -- the Unix file attributes
    TreeEntry.to_object() -- returns the git object (equivalent to repo[entry.oid])


.. autoclass:: pygit2.Tree
   :members:
   :show-inheritance:
   :undoc-members:

.. autoclass:: pygit2.TreeEntry
   :members:
   :show-inheritance:
   :undoc-members:


Blobs
-----------------

A blob is equivalent to a file in a file system.::

    >>> # create a blob out of memory
    >>> oid  = repo.create_blob('foo bar')
    >>> blob = repo[oid]
    >>> blob.data
    'foo bar'
    >>> oid
    '\x96\xc9\x06um{\x91\xc4S"a|\x92\x95\xe4\xa8\rR\xd1\xc5'

.. autoclass:: pygit2.Blob
   :members:
   :show-inheritance:
   :undoc-members:


Tags
-----------------

A tag is a static label for a commit. See references for more information.


.. autoclass:: pygit2.Tag
   :members:
   :show-inheritance:
   :undoc-members: