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Filename : roundtrip.py
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# Copyright (C) 2010-2018 Jelmer Vernooij <jelmer@jelmer.uk>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

"""Roundtripping support.

Bazaar stores more data than Git, which means that in order to preserve
a commit when it is pushed from Bazaar into Git we have to stash
that extra metadata somewhere.

There are two kinds of metadata relevant here:
 * per-file metadata (stored by revision+path)
  - usually stored per tree
 * per-revision metadata (stored by git commit id)

Bazaar revisions have the following information that is not
present in Git commits:
 * revision ids
 * revision properties
 * ghost parents

Tree content:
 * empty directories
 * path file ids
 * path last changed revisions [1]

 [1] path last changed revision information can usually
     be induced from the existing history, unless
     ghost revisions are involved.

This extra metadata is stored in so-called "supplements":
  * CommitSupplement
  * TreeSupplement
"""

from io import BytesIO

from .. import osutils


class CommitSupplement:
    """Supplement for a Bazaar revision roundtripped into Git.

    :ivar revision_id: Revision id, as string
    :ivar properties: Revision properties, as dictionary
    :ivar explicit_parent_ids: Parent ids (needed if there are ghosts)
    :ivar verifiers: Verifier information
    """

    revision_id = None

    explicit_parent_ids = None

    def __init__(self):
        self.properties = {}
        self.verifiers = {}

    def __nonzero__(self):
        return bool(self.revision_id or self.properties or self.explicit_parent_ids)


class TreeSupplement:
    """Supplement for a Bazaar tree roundtripped into Git.

    This provides file ids (if they are different from the mapping default)
    and can provide text revisions.
    """


def parse_roundtripping_metadata(text):
    """Parse Bazaar roundtripping metadata."""
    ret = CommitSupplement()
    f = BytesIO(text)
    for l in f.readlines():
        (key, value) = l.split(b":", 1)
        if key == b"revision-id":
            ret.revision_id = value.strip()
        elif key == b"parent-ids":
            ret.explicit_parent_ids = tuple(value.strip().split(b" "))
        elif key == b"testament3-sha1":
            ret.verifiers[b"testament3-sha1"] = value.strip()
        elif key.startswith(b"property-"):
            name = key[len(b"property-") :]
            if name not in ret.properties:
                ret.properties[name] = value[1:].rstrip(b"\n")
            else:
                ret.properties[name] += b"\n" + value[1:].rstrip(b"\n")
        else:
            raise ValueError
    return ret


def generate_roundtripping_metadata(metadata, encoding):
    """Serialize the roundtripping metadata.

    :param metadata: A `CommitSupplement` instance
    :return: String with revision metadata
    """
    lines = []
    if metadata.revision_id:
        lines.append(b"revision-id: %s\n" % metadata.revision_id)
    if metadata.explicit_parent_ids:
        lines.append(b"parent-ids: %s\n" % b" ".join(metadata.explicit_parent_ids))
    for key in sorted(metadata.properties.keys()):
        for l in metadata.properties[key].split(b"\n"):
            lines.append(b"property-%s: %s\n" % (key, osutils.safe_utf8(l)))
    if b"testament3-sha1" in metadata.verifiers:
        lines.append(b"testament3-sha1: %s\n" % metadata.verifiers[b"testament3-sha1"])
    return b"".join(lines)


def extract_bzr_metadata(message):
    """Extract Bazaar metadata from a commit message.

    :param message: Commit message to extract from
    :return: Tuple with original commit message and metadata object
    """
    split = message.split(b"\n--BZR--\n", 1)
    if len(split) != 2:
        return message, None
    return split[0], parse_roundtripping_metadata(split[1])


def inject_bzr_metadata(message, commit_supplement, encoding):
    if not commit_supplement:
        return message
    rt_data = generate_roundtripping_metadata(commit_supplement, encoding)
    if not rt_data:
        return message
    if not isinstance(rt_data, bytes):
        raise TypeError(rt_data)
    return message + b"\n--BZR--\n" + rt_data