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Commit 6f237f22 authored by Kirill Smelkov's avatar Kirill Smelkov
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git-backup: Initial draft 

This program backups files and set of bare Git repositories into one Git repository.
Files are copied to blobs and then added to tree under certain place, and for
Git repositories, all reachable objects are pulled in with maintaining index
which remembers reference -> sha1 for every pulled repositories.

After objects from backuped Git repositories are pulled in, we create new
commit which references tree with changed backup index and files, and also has
all head objects from pulled-in repositories in its parents(*). This way backup
has history and all pulled objects become reachable from single head commit in
backup repository. In particular that means that the whole state of backup can
be described with only single sha1, and that backup repository itself could be
synchronized via standard git pull/push, be repacked, etc.

Restoration process is the opposite - from a particular backup state, files are
extracted at a proper place, and for Git repositories a pack with all objects
reachable from that repository heads is prepared and extracted from backup
repository object database.

This approach allows to leverage Git's good ability for object contents
deduplication and packing, especially for cases when there are many hosted
repositories which are forks of each other with relatively minor changes in
between each other and over time, and mostly common base. In author experience
the size of backup is dramatically smaller compared to straightforward "let's
tar it all" approach.

Data for all backuped files and repositories can be accessed if one has access
to backup repository, so either they all should be in the same security domain,
or extra care has to be taken to protect access to backup repository.

File permissions are not managed with strict details due to inherent
nature of Git. This aspect can be improved with e.g. etckeeper-like
(http://etckeeper.branchable.com/) approach if needed.

Please see README.txt with user-level overview on how to use git-backup.

NOTE the idea of pulling all refs together is similar to git-namespaces
     http://git-scm.com/docs/gitnamespaces

(*) Tag objects are handled specially - because in a lot of places Git insists and
    assumes commit parents can only be commit objects. We encode tag objects in
    specially-crafted commit object on pull, and decode back on backup restore.

    We do likewise if a ref points to tree or blob, which is valid in Git.
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Copyright (C) <year> <name of author>
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 3 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, see <http://www.gnu.org/licenses/>.
Also add information on how to contact you by electronic and paper mail.
If the program does terminal interaction, make it output a short
notice like this when it starts in an interactive mode:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, your program's commands
might be different; for a GUI interface, you would use an "about box".
You should also get your employer (if you work as a programmer) or school,
if any, to sign a "copyright disclaimer" for the program, if necessary.
For more information on this, and how to apply and follow the GNU GPL, see
<http://www.gnu.org/licenses/>.
The GNU General Public License does not permit incorporating your program
into proprietary programs. If your program is a subroutine library, you
may consider it more useful to permit linking proprietary applications with
the library. If this is what you want to do, use the GNU Lesser General
Public License instead of this License. But first, please read
<http://www.gnu.org/philosophy/why-not-lgpl.html>.
README.txt 0 → 100644
View file @ 6f237f22
=======================================================================
Git-backup - Backup set of Git repositories & just files; efficiently
=======================================================================
:author: Kirill Smelkov <kirr@nexedi.com>
:date: 2015 Aug 31
This program backups files and set of bare Git repositories into one Git repository.
Files are copied to blobs and then added to tree under certain place, and for
Git repositories, all reachable objects are pulled in with maintaining index
which remembers reference -> sha1 for all pulled repositories.
This allows to leverage Git's good data deduplication ability, especially for
cases when there are many hosted repositories which are forks of each other,
and for backup to have history and be otherwise managed as a usual Git
repository. In particular it is possible to use standard git pull/push to
synchronize backups in several places.
Backup workflow is:
1. create backup repository::
$ mkdir backup
$ cd backup
$ git init # both bare and non-bare possible
2. pull files and Git repositories into backup repository::
$ git-backup pull dir1:prefix1 dir2:prefix2 ...
This will pull bare Git repositories & just files from `dir1` into backup
under `prefix1`, from `dir2` into backup prefix `prefix2`, etc...
3. restore files and Git repositories from backup::
$ git-backup restore <backup-state-sha1> prefix1:dir1
Restore Git repositories & just files from backup `prefix1` into `dir1`,
from backup `prefix2` into `dir2`, etc...
Backup state to restore is taken from <backup-state-sha1> which is sha1 or
ref pointing to backup repository state.
4. backup repository itself can be managed with Git. In particular it can be
synchronized between several places with standard git pull/push, be
repacked, etc::
$ git push ...
$ git pull ...
Please see `git-backup` source with technical overview on how it works.
git-backup 0 → 100755
View file @ 6f237f22
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (C) 2015 Nexedi SA and Contributors.
# Kirill Smelkov <kirr@nexedi.com>
#
# This program is free software: you can Use, Study, Modify and Redistribute
# it under the terms of the GNU General Public License version 3, or (at your
# option) any later version, as published by the Free Software Foundation.
#
# This program is distributed WITHOUT ANY WARRANTY; without even the implied
# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
#
# See COPYING file for full licensing terms.
"""Git-backup - Backup set of Git repositories & just files; efficiently
This program backups files and set of bare Git repositories into one Git repository.
Files are copied to blobs and then added to tree under certain place, and for
Git repositories, all reachable objects are pulled in with maintaining index
which remembers reference -> sha1 for every pulled repositories.
After objects from backuped Git repositories are pulled in, we create new
commit which references tree with changed backup index and files, and also has
all head objects from pulled-in repositories in its parents(*). This way backup
has history and all pulled objects become reachable from single head commit in
backup repository. In particular that means that the whole state of backup can
be described with only single sha1, and that backup repository itself could be
synchronized via standard git pull/push, be repacked, etc.
Restoration process is the opposite - from a particular backup state, files are
extracted at a proper place, and for Git repositories a pack with all objects
reachable from that repository heads is prepared and extracted from backup
repository object database.
This approach allows to leverage Git's good ability for object contents
deduplication and packing, especially for cases when there are many hosted
repositories which are forks of each other with relatively minor changes in
between each other and over time, and mostly common base. In author experience
the size of backup is dramatically smaller compared to straightforward "let's
tar it all" approach.
Data for all backuped files and repositories can be accessed if one has access
to backup repository, so either they all should be in the same security domain,
or extra care has to be taken to protect access to backup repository.
File permissions are not managed with strict details due to inherent
nature of Git. This aspect can be improved with e.g. etckeeper-like
(http://etckeeper.branchable.com/) approach if needed.
Please see README.txt with user-level overview on how to use git-backup.
NOTE the idea of pulling all refs together is similar to git-namespaces
http://git-scm.com/docs/gitnamespaces
(*) Tag objects are handled specially - because in a lot of places Git insists and
assumes commit parents can only be commit objects. We encode tag objects in
specially-crafted commit object on pull, and decode back on backup restore.
We do likewise if a ref points to tree or blob, which is valid in Git.
"""
import os
import sys
from os.path import join as pathjoin, exists as pathexists, dirname
from time import strftime
from subprocess import Popen, PIPE
from stat import S_ISLNK
from getopt import getopt, GetoptError
from errno import EEXIST
from urllib import quote, unquote
# verbose output
# 0 - silent
# 1 - info
# 2 - progress of long-running operations
# 3 - debug
verbose = 1
def info(msg):
if verbose > 0:
print(msg)
# what to pass to git subprocess to stdout/stderr
# None - no-redirection, PIPE - output to us
def gitprogress():
return None if verbose > 1 else PIPE
def debug(msg):
if verbose > 2:
print(msg)
# run `git *argv` -> retcode, stdout, stderr
# **kw can be: stdin=... stdout,stderr=PIPE|None raw=True|False env=dict|None
def git(*argv, **kw):
argv = ['git'] + list(argv)
stdin = kw.pop('stdin', None)
stdout = kw.pop('stdout', PIPE)
stderr = kw.pop('stderr', PIPE)
raw = kw.pop('raw', False)
env = kw.pop('env', None)
if kw:
raise RuntimeError('git: unsupported kwargs: %s' % kw)
debug(' '.join(argv))
p = Popen(argv, stdin=PIPE, stdout=stdout, stderr=stderr, env=env)
stdout, stderr = p.communicate(stdin)
if not raw:
# prettify stdout (e.g. so that 'sha1\n' becomes 'sha1' and can be used directly
if stdout is not None:
stdout = stdout.strip()
if stderr is not None:
stderr = stderr.strip()
return p.returncode, stdout, stderr
# run `git *argv` -> stdout
# on error - raise exception
def xgit(*argv, **kw):
retcode, stdout, stderr = git(*argv, **kw)
if retcode:
raise RuntimeError('git ' + ' '.join(argv) + '\n' + (stderr and stderr or '(failed)'))
return stdout
# like os.walk() but raise on error + entries are emitted in sorted order
def reraise(e): raise e
def xwalk(top):
for dirpath, dirnames, filenames in os.walk(top, onerror=reraise):
dirnames.sort(); filenames.sort()
yield dirpath, dirnames, filenames
# strip_prefix('/a/b', '/a/b/c/d/e') -> 'c/d/e' (without leading /)
def strip_prefix(prefix, path):
assert path.startswith(prefix)
path = path[len(prefix):]
while path.startswith('/'):
path = path[1:] # strip leading /
return path
# reprefix('/a', '/b', '/a/str') -> '/b/str'
def reprefix(prefix_from, prefix_to, path):
path = strip_prefix(prefix_from, path)
return '%s/%s' % (prefix_to, path)
# remove all occurrences of item in seq
def removeall(seq, item):
while item in seq:
seq.remove(item)
# mkdir -p
def mkdir_p(path):
try:
os.makedirs(path)
except OSError as e:
if e.errno != EEXIST:
raise
# file -> blob_sha1, mode
def file_to_blob(path):
argv = ['hash-object', '-w', '--no-filters']
st = os.lstat(path)
if S_ISLNK(st.st_mode):
# git hash-object does not handle symlinks
argv += ['--stdin']
stdin = os.readlink(path)
else:
argv += ['--', path]
stdin = None
blob_sha1 = xgit(*argv, stdin=stdin)
return blob_sha1, st.st_mode
# blob_sha1, mode -> file
def blob_to_file(blob_sha1, mode, path):
blob_content = xgit('cat-file', 'blob', blob_sha1, raw=True)
mkdir_p(dirname(path))
if S_ISLNK(mode):
os.symlink(blob_content, path)
else:
with open(path, 'wb') as f:
f.write(blob_content)
os.fchmod(f.fileno(), mode)
# create empty git tree -> tree sha1
tree_empty = None
def mktree_empty():
global tree_empty
if not tree_empty:
tree_empty = xgit('mktree', stdin='')
return tree_empty
# `git commit-tree` -> commit_sha1, raise on error
def xcommit_tree(tree, parents, msg, author={}, committer={}):
argv = ['commit-tree', tree]
for _ in parents:
argv += ['-p', _]
env = os.environ.copy()
if author.get('name'): env['GIT_AUTHOR_NAME'] = author['name']
if author.get('email'): env['GIT_AUTHOR_EMAIL'] = author['email']
if author.get('date'): env['GIT_AUTHOR_DATE'] = author['date']
if committer.get('name'): env['GIT_COMMITTER_NAME'] = committer['name']
if committer.get('email'): env['GIT_COMMITTER_EMAIL'] = committer['email']
if committer.get('date'): env['GIT_COMMITTER_DATE'] = committer['date']
return xgit(*argv, stdin=msg, env=env)
# parse tag object -> tagged_type, tagged_sha1
def tag_info(tag_raw):
_ = tag_raw.splitlines()
_sha1 = _[0] # object 7ecec52d42a964c4a8e9f6ca41bb0b5ce00049b4
_type = _[1] # type commit
_, tagged_sha1 = _sha1.split()
if _ != 'object':
raise RuntimeError("E: expected 'object' got %r" % _)
_, tagged_type = _type.split()
if _ != 'type':
raise RuntimeError("E: expected 'type' got %r" % _)
return tagged_type, tagged_sha1
# represent tag/tree/blob as specially crafted commit
#
# The reason we do this is that we want refs/tag/* to be parents of synthetic
# backup commit, but git does not allow tag objects to be in commit parents.
# Also besides commit and tag, it is possible for a ref to point to a tree or blob.
#
# We always attach original tagged object to crafted commit in one way or
# another, so that on backup restore we only have to recreate original tag
# object and tagged object is kept there in repo thanks to it being reachable
# through created commit.
def obj_represent_as_commit(sha1, obj_type=None):
if obj_type is None:
obj_type = xgit('cat-file', '-t', sha1)
if obj_type not in ('tag', 'tree', 'blob'):
raise RuntimeError('E: cannot encode %s as commit' % obj_type)
# first line in commit msg = object type
obj_encoded = '%s\n' % obj_type
# below the code layout is mainly for tag type, and we hook tree and blob
# types handling into that layout
if obj_type == 'tag':
tag_raw = xgit('cat-file', 'tag', sha1, raw=True)
tagged_type, tagged_sha1 = tag_info(tag_raw)
obj_encoded += tag_raw
else:
# for tree/blob we only care that object stays reachable
tagged_type = obj_type
tagged_sha1 = sha1
# all commits we do here - we do with fixed name/date, so transformation
# tag->commit is stable wrt git environment and time change
fixed = {'name': 'Git backup', 'email': 'git@backup.org', 'date': '@0 +0000'}
def zcommit_tree(tree, parents, msg):
return xcommit_tree(tree, parents, msg, author=fixed, committer=fixed)
# Tag ~> Commit*
# | .msg: Tag
# v .tree -> ø
# Commit .parent -> Commit
if tagged_type == 'commit':
return zcommit_tree(mktree_empty(), [tagged_sha1], obj_encoded)
# Tag ~> Commit*
# | .msg: Tag
# v .tree -> Tree
# Tree .parent -> ø
if tagged_type == 'tree':
return zcommit_tree(tagged_sha1, [], obj_encoded)
# Tag ~> Commit*
# | .msg: Tag
# v .tree -> Tree* "tagged" -> Blob
# Blob .parent -> ø
if tagged_type == 'blob':
tree_for_blob = xgit('mktree', stdin='100644 blob %s\ttagged\n' % tagged_sha1)
return zcommit_tree(tree_for_blob, [], obj_encoded)
# Tag₂ ~> Commit₂*
# | .msg: Tag₂
# v .tree -> ø
# Tag₁ .parent -> Commit₁*
if tagged_type == 'tag':
commit1 = obj_represent_as_commit(tagged_sha1, tagged_type)
return zcommit_tree(mktree_empty(), [commit1], obj_encoded)
raise RuntimeError('E: Unknown tagged type %r in %s' % (tagged_type, sha1))
# recreate tag/tree/blob from specially crafted commit
# (see obj_represent_as_commit() about how a objects are originally translated into commit)
def obj_recreate_from_commit(commit_sha1):
# extract .tree .parent[] and .msg
#
# unfortunately `git show --format=%B` adds newline and optionally wants to
# reencode commit message and otherwise heavily rely on rev-list traversal
# machinery -> so we decode commit by hand in a plumbing way.
commit_raw = xgit('cat-file', 'commit', commit_sha1, raw=True)
msg_start = commit_raw.index('\n\n')
msg = commit_raw[msg_start+2:]
head = commit_raw[:msg_start+1]
tree = None
parent = None
for _ in head.splitlines():
if _.startswith('tree '):
if tree:
raise RuntimeError('E: multiple tree in commit %s' % commit_sha1)
_, tree = _.split()
continue
if _.startswith('parent '):
if parent:
raise RuntimeError('E: encoded obj has >1 parents in commit %s' % commit_sha1)
_, parent = _.split()
continue
if not tree:
raise RuntimeError('E: no tree in commit %s' % commit_sha1)
obj_type, _, obj_raw = msg.partition('\n')
if obj_type not in ('tag', 'tree', 'blob'):
raise RuntimeError('E: unexpected encoded object type %r in %s' % (obj_type, commit_sha1))
# for tree/blob we do not need to do anything - that objects were reachable
# from commit and are present in git db.
if obj_type in ('tree', 'blob'):
return
# re-create tag object
tag_sha1 = xgit('hash-object', '-t', 'tag', '-w', '--stdin', stdin=obj_raw)
# the original tagged object should be already in repository, because we
# always attach it to encoding commit one way or another,
# except we need to recurse, if it was Tag₂->Tag₁
tagged_type, _ = tag_info(obj_raw)
if tagged_type == 'tag':
assert parent is not None
obj_recreate_from_commit(parent)
# verify consistency via re-encoding tag again
commit_sha1_ = obj_represent_as_commit(tag_sha1, 'tag')
if commit_sha1_ != commit_sha1:
raise RuntimeError('E: tag encoded by commit %s corrupt (reencoded as %s)' %
(commit_sha1, commit_sha1_))
# git-backup pull
def cmd_pull_usage(f):
print >>f, \
"""git-backup pull <dir1>:<prefix1> <dir2>:<prefix2> ...
Pull bare Git repositories & just files from dir1 into backup prefix1,
from dir2 into backup prefix2, etc...
"""
def cmd_pull(argv):
try:
optv, argv = getopt(argv, "h", ["help"])
except GetoptError as e:
print(e)
cmd_pull_usage(sys.stderr)
exit(1)
for opt, arg in optv:
if opt in ("-h", "--help"):
cmd_pull_usage(sys.stdout)
exit(0)
if not argv:
cmd_pull_usage(sys.stderr)
exit(1)
pullspecv = [] # [] of (dir,prefix)
for _ in argv:
try:
dir_, prefix = _.split(':')
except ValueError:
print >>sys.stderr, "E: invalid pullspec '%s'" % _
cmd_pull_usage(sys.stderr)
exit(1)
pullspecv.append( (dir_, prefix) )
cmd_pull_(pullspecv)
def cmd_pull_(pullspecv):
# while pulling, we'll keep refs from all pulled repositories under temp
# unique work refs namespace.
backup_time = strftime('%Y%m%d-%H%M')
backup_refs_work = 'refs/backup/%s/' % backup_time # refs/backup/20150820-2109/
backup_lock = 'refs/backup.locked'
# make sure another `git-backup pull` is not running
xgit('update-ref', backup_lock, mktree_empty(), '00'*20)
# make sure there is root commit
st, _, _ = git('rev-parse', '--verify', 'HEAD')
if st:
info('# creating root commit')
# NOTE `git commit` does not work in bare repo - do commit by hand
commit = xcommit_tree(mktree_empty(), [], 'Initialize git-backup repository')
xgit('update-ref', '-m', 'git-backup pull init', 'HEAD', commit)
# walk over specified dirs, pulling objects from git and adding non-git-object files
for dir_, prefix in pullspecv:
# make sure index is empty for prefix (so that we start from clean
# prefix namespace and this way won't leave stale removed things)
xgit('rm', '--cached', '-r', '--ignore-unmatch', '--', prefix)
for dirpath, dirnames, filenames in xwalk(dir_):
# files -> add directly to index to commit later
for _ in filenames:
filepath = pathjoin(dirpath, _)
info('# file %s\t<- %s' % (prefix, filepath))
blob, mode = file_to_blob(filepath)
xgit('update-index', '--add', '--cacheinfo', '%o,%s,%s' % \
(mode, blob, reprefix(dir_, prefix, filepath)) )
# directories -> look for *.git and handle git object specially
for i, dirname in enumerate(dirnames):
# do not recurse into *.git/objects/ - we'll save them specially
if dirpath.endswith('.git') and dirname == 'objects':
dirnames[i] = None
continue
# else we recurse, but handle *.git specially - via fetching objects from it
if not dirname.endswith('.git'):
continue
# git repo - let's pull all refs from it to our backup refs namespace
gitrepo = pathjoin(dirpath, dirname)
info('# git %s\t<- %s' % (prefix, gitrepo))
# NOTE --no-tags : do not try to autoextend commit -> covering tag
xgit('fetch', '--no-tags', gitrepo,
'refs/*:%s%s/*' % (backup_refs_work,
# NOTE repo name is quoted as it can contain spaces, and refs must not
quote(reprefix(dir_, prefix, gitrepo))),
# TODO do not show which ref we pulled - show only pack transfer progress
stderr=gitprogress())
# XXX do we want to fsck source git repo on pull ?
# do not recurse into dirs so marked
removeall(dirnames, None)
# all refs from all found git repositories populated.
# now prepare manifest with ref -> sha1 and do a synthetic commit merging all that sha1
# (so they become all reachable from HEAD -> survive repack and be transferable on git pull)
#
# NOTE we handle tag/tree/blob objects specially - because these objects cannot
# be in commit parents, we convert them to specially-crafted commits and use them.
# The commits prepared contain full info how to restore origianl objects.
# backup.refs format:
#
# 1eeb0324 <prefix>/wendelin.core.git/heads/master
# 213a9243 <prefix>/wendelin.core.git/tags/v0.4 <213a9243-converted-to-commit>
# ...
#
# NOTE `git for-each-ref` sorts output by ref
# -> backup_refs is sorted and stable between runs
backup_refs_list = xgit('for-each-ref', backup_refs_work)
backup_refs = [] # backup.refs content
backup_refs_parents = set() # sha1 for commit parents, obtained from refs
noncommit_seen = {} # {} sha1 -> sha1_ (there are many duplicate tags)
for _ in backup_refs_list.splitlines():
sha1, type_, ref = _.split()
backup_refs_entry = '%s %s' % (sha1, strip_prefix(backup_refs_work, ref))
# represent tag/tree/blob as specially crafted commit, because we
# cannot use it as commit parent.
sha1_ = sha1
if type_ != 'commit':
#info('obj_as_commit %s %s\t%s' % (sha1, type_, ref)) XXX
sha1_ = noncommit_seen.get(sha1)
if sha1_ is None:
sha1_ = obj_represent_as_commit(sha1, type_)
noncommit_seen[sha1] = sha1_
backup_refs_entry += ' %s' % sha1_
backup_refs.append(backup_refs_entry)
if sha1_ not in backup_refs_parents: # several refs can refer to the same sha1
backup_refs_parents.add(sha1_)
backup_refs = '\n'.join(backup_refs)
backup_refs_parents = list(backup_refs_parents)
backup_refs_parents.sort() # so parents order is stable in between runs
# backup_refs -> blob
backup_refs_sha1 = xgit('hash-object', '-w', '--stdin', stdin=backup_refs)
# add backup_refs blob to index
xgit('update-index', '--add', '--cacheinfo', '100644,%s,backup.refs' % backup_refs_sha1)
# index is ready - prepare tree and commit
backup_tree_sha1 = xgit('write-tree')
HEAD = xgit('rev-parse', 'HEAD')
commit_sha1 = xcommit_tree(backup_tree_sha1, [HEAD] + backup_refs_parents,
'Git-backup %s' % backup_time)
xgit('update-ref', '-m', 'git-backup pull', 'HEAD', commit_sha1, HEAD)
# remove no-longer needed backup refs & verify they don't stay
backup_refs_delete = ''
for _ in backup_refs_list.splitlines():
sha1, type_, ref = _.split()
backup_refs_delete += 'delete %s %s\n' % (ref, sha1)
xgit('update-ref', '--stdin', stdin=backup_refs_delete)
_ = xgit('for-each-ref', backup_refs_work)
if _:
raise RuntimeError('Backup refs under %s not deleted properly' % backup_refs_work)
# if we have working copy - update it
bare = xgit('rev-parse', '--is-bare-repository')
bare = (bare == 'true')
if not bare:
# `git checkout-index -af` -- does not delete deleted files
# `git read-tree -v -u --reset HEAD~ HEAD` -- needs index matching
# original worktree to properly work, but we already have updated index
#
# so we get changes we committed as diff and apply to worktree
diff = xgit('diff', '--binary', HEAD, 'HEAD', raw=True)
if diff:
diffstat = xgit('apply', '--stat', '--apply', '--binary', '--whitespace=nowarn',
stdin=diff, raw=True)
info(diffstat)
# we are done - unlock
xgit('update-ref', '-d', backup_lock)
# git-backup restore
def cmd_restore_usage(f):
print >>f, \
"""git-backup restore <commit-ish> <prefix1>:<dir1> <prefix2>:<dir2> ...
Restore Git repositories & just files from backup prefix1 into dir1,
from backup prefix2 into dir2, etc...
Backup state to restore is taken from <commit-ish>.
"""
def cmd_restore(argv):
try:
optv, argv = getopt(argv, "h", ["help"])
except GetoptError as e:
print(e)
cmd_restore_usage(sys.stderr)
exit(1)
for opt, arg in optv:
if opt in ("-h", "--help"):
cmd_restore_usage(sys.stdout)
exit(0)
if len(argv) < 2:
cmd_restore_usage(sys.stderr)
exit(1)
HEAD = argv[0]
restorespecv = [] # [] of (prefix,dir)
for _ in argv[1:]:
try:
prefix, dir_ = _.split(':')
except ValueError:
print >>sys.stderr, "E: invalid restorespec '%s'" % _
cmd_restore_usage(sys.stderr)
exit(1)
restorespecv.append( (prefix, dir_) )
cmd_restore_(HEAD, restorespecv)
# kirr/wendelin.core.git/heads/master -> kirr/wendelin.core.git
# tiwariayush/Discussion%20Forum%20.git/... -> tiwariayush/Discussion Forum .git
def ref_to_repo(ref):
dotgit = ref.find('.git/')
if dotgit == -1:
raise RuntimeError('E: %s is not a ref for a git repo')
repo = ref[:dotgit+4]
repo = unquote(repo) # unquote repo name we originally quoted when making backup
return repo
# sha1 value(s) for a ref in 'backup.refs'
class BackupRefSha1:
# .sha1 -- original sha1 this ref was pointing to in original repo
# .sha1_ -- sha1 actually used to represent sha1's object in backup repo
# (for tag/tree/blob - they are converted to commits)
def __init__(self, sha1, sha1_):
self.sha1 = sha1
self.sha1_ = sha1_
def cmd_restore_(HEAD, restorespecv):
HEAD = xgit('rev-parse', '--verify', HEAD)
# read backup refs index
backup_refs = {} # prefix+ref -> BackupRefSha1
backup_refs_ = xgit('cat-file', 'blob', '%s:backup.refs' % HEAD)
for _ in backup_refs_.splitlines():
# sha1 prefix+refname (sha1_)
refentryv = _.split()
if len(refentryv) not in (2,3):
raise RuntimeError('E: invalid entry in backup.refs: %s' % _)
sha1, ref = refentryv[:2]
sha1_ = refentryv[2] if len(refentryv) == 3 else sha1
if ref in backup_refs:
raise RuntimeError('E: duplicate ref %s in backup.refs' % ref)
backup_refs[ref] = BackupRefSha1(sha1, sha1_)
# walk over specified prefixes restoring files and packs in *.git
for prefix, dir_ in restorespecv:
if pathexists(dir_):
raise RuntimeError('E: %s already exists' % dir_)
# files
lstree = xgit('ls-tree', '--full-tree', '-r', '-z', '--', HEAD, prefix, raw=True)
for _ in lstree.split('\0'):
if not _:
continue # last empty line after last \0
# NOTE maxsplit=3 because filename can contain spaces
mode, type_, sha1, filename = _.split(None, 3)
assert type_ == 'blob'
mode = int(mode, 8)
filename = reprefix(prefix, dir_, filename)
info('# file %s\t-> %s' % (prefix, filename))
blob_to_file(sha1, mode, filename)
# git packs
refs = set(_ for _ in backup_refs.keys() if _.startswith('%s/' % prefix))
repos = set(ref_to_repo(_) for _ in refs)
for repo in sorted(repos): # NOTE sorted - to process repos always in the same order
repopath = reprefix(prefix, dir_, repo)
info('# git %s\t-> %s' % (prefix, repopath))
# make sure git will recognize this dir as repo
# (refs could all be packed and thus no heads/ and tags/ dirs created on files restore)
mkdir_p('%s/refs/heads' % repopath)
mkdir_p('%s/refs/tags' % repopath)
# {} ref -> BackupRefSha1 for this repo
repo_refs = dict((reprefix(repo, 'refs', _), backup_refs[_])
for _ in refs if _.startswith(repo))
# make sure tag/tree/blob objects represented as commits are
# present, before we generate pack for restored repo.
# ( such objects could be lost e.g. after backup repo repack as they
# are not reachable from backup repo HEAD )
for _ in repo_refs.values():
if _.sha1 != _.sha1_:
obj_recreate_from_commit(_.sha1_)
# extract pack for that repo from big backup pack + decoded tags
mkdir_p('%s/objects/pack' % repopath)
pack_argv = ['pack-objects',
'--revs', # include all objects referencable from input sha1 list
'--reuse-object', '--reuse-delta', '--delta-base-offset']
if not verbose:
pack_argv += ['-q']
pack_argv += ['%s/objects/pack/pack' % repopath]
repo_sha1_heads = '\n'.join(set(_.sha1 for _ in repo_refs.values()))
xgit(*pack_argv, stdin=repo_sha1_heads, stderr=gitprogress())
# verify that extracted repo refs match backup.refs index after extraction
x_ref_list = xgit('--git-dir=%s' % repopath,
'for-each-ref', '--format=%(objectname) %(refname)')
repo_ref_list = '\n'.join( ['%s %s' % (repo_refs[_].sha1, _)
for _ in sorted(repo_refs)] )
if x_ref_list != repo_ref_list:
raise RuntimeError('E: extracted repository refs corrupt')
# check connectivity in recreated repository.
#
# This way we verify that extracted pack indeed contains all
# objects for all refs in the repo.
#
# Compared to fsck we do not re-compute sha1 sum of objects which
# is significantly faster.
x_heads_sha1 = set(_.sha1 for _ in repo_refs.values())
x_heads_sha1 = '\n'.join(x_heads_sha1)
try:
xgit('--git-dir=%s' % repopath,
'rev-list', '--objects', '--stdin', '--quiet', stdin=x_heads_sha1)
except:
print >>sys.stderr, 'E: Problem while checking connectivity of extracted repo:'
raise
# XXX disabled because it is slow
# # NOTE progress goes to stderr, problems go to stdout
# xgit('--git-dir=%s' % repopath, 'fsck',
# # only check that traversal from refs is ok: this unpacks
# # commits and trees and verifies blob objects are there,
# # but do _not_ unpack blobs =fast.
# '--connectivity-only',
# stdout=gitprogress(), stderr=gitprogress())
commands = {
'pull': cmd_pull,
'restore': cmd_restore,
}
def usage(f):
print >>f, \
"""git-backup [options] <command>
pull pull git-repositories and files to backup
restore restore git-repositories and files from backup
common options:
-h --help this help text.
-v --verbose increase verbosity.
-q --quiet decrease verbosity.
"""
def main():
global verbose
try:
optv, argv = getopt(sys.argv[1:], "hvq", ["help", "verbose", "quiet"])
except GetoptError as e:
print(e)
usage(sys.stderr)
exit(1)
for opt, arg in optv:
if opt in ("-h", "--help"):
usage(sys.stdout)
exit(0)
elif opt in ("-v", "--verbose"):
verbose += 1
elif opt in ("-q", "--quiet"):
verbose -= 1
if not argv:
usage(sys.stderr)
exit(1)
cmd = commands.get(argv[0])
if not cmd:
print >>sys.stderr, "E: unknown command %r" % argv[0]
exit(1)
cmd(argv[1:])
if __name__ == '__main__':
main()
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