The most important optimization for performance when repacking is the
ability to reuse data from a previous pack as is and bypass any delta
or even SHA1 computation by simply copying the raw data from one pack
to another directly.
The problem with this is that any data corruption within a copied object
would go unnoticed and the new (repacked) pack would be self-consistent
with its own checksum despite containing a corrupted object. This is a
real issue that already happened at least once in the past.
In some attempt to prevent this, we validate the copied data by inflating
it and making sure no error is signaled by zlib. But this is still not
perfect as a significant portion of a pack content is made of object
headers and references to delta base objects which are not deflated and
therefore not validated when repacking actually making the pack data reuse
still not as safe as it could be.
Of course a full SHA1 validation could be performed, but that implies
full data inflating and delta replaying which is extremely costly, which
cost the data reuse optimization was designed to avoid in the first place.
So the best solution to this is simply to store a CRC32 of the raw pack
data for each object in the pack index. This way any object in a pack can
be validated before being copied as is in another pack, including header
and any other non deflated data.
Why CRC32 instead of a faster checksum like Adler32? Quoting Wikipedia:
Jonathan Stone discovered in 2001 that Adler-32 has a weakness for very
short messages. He wrote "Briefly, the problem is that, for very short
packets, Adler32 is guaranteed to give poor coverage of the available
bits. Don't take my word for it, ask Mark Adler. :-)" The problem is
that sum A does not wrap for short messages. The maximum value of A for
a 128-byte message is 32640, which is below the value 65521 used by the
modulo operation. An extended explanation can be found in RFC 3309,
which mandates the use of CRC32 instead of Adler-32 for SCTP, the
Stream Control Transmission Protocol.
In the context of a GIT pack, we have lots of small objects, especially
deltas, which are likely to be quite small and in a size range for which
Adler32 is dimed not to be sufficient. Another advantage of CRC32 is the
possibility for recovery from certain types of small corruptions like
single bit errors which are the most probable type of corruptions.
OK what this patch does is to compute the CRC32 of each object written to
a pack within pack-objects. It is not written to the index yet and it is
obviously not validated when reusing pack data yet either.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Change a few size and offset variables to more appropriate type, then
add overflow tests on those offsets. This prevents any bad data to be
generated/processed if off_t happens to not be large enough to handle
some big packs.
Better be safe than sorry.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch introduces the MSB() macro to obtain the desired number of
most significant bits from a given variable independently of the variable
type.
It is then used to better implement the overflow test on the OBJ_OFS_DELTA
base offset variable with the property of always working correctly
regardless of the type/size of that variable.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The coming index format change doesn't allow for the number of objects
to be determined from the size of the index file directly. Instead, Let's
initialize a field in the packed_git structure with the object count when
the index is validated since the count is always known at that point.
While at it let's reorder some struct packed_git fields to avoid padding
due to needed 64-bit alignment for some of them.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This just makes sure that when we do a read_directory(), we check
that the filename fits in the buffer we allocated (with a bit of
slop)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The diff helpers used to do the magic mode canonicalization and all the
other special mode handling by hand ("trust executable bit" and "has
symlink support" handling).
That's bogus. Use "ce_mode_from_stat()" that does this all for us.
This is also going to be required when we add support for links to other
git repositories.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Use the comment in the code to document the --exclude-existing
function to git-show-ref.
Signed-off-by: Julian Phillips <julian@quantumfyre.co.uk>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Unlike 'patch --fuzz=NUM', which specifies the number of lines allowed
to mismatch, 'git-apply -CNUM' requests the match of NUM lines of
context. Omitting -C requests full context match, and that's what
should be used for cvsexportcommit -p.
Signed-off-by: Junio C Hamano <junkio@cox.net>
As noted by Junio, --format=tar should be assumed if no format
was specified.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>
* jc/merge-subtree:
A new merge stragety 'subtree'.
It is safe to merge this early as this is a feature that user
explicitly needs to ask for and would not trigger otherwise. A
known issue with the current implementation is that the subtree
matching heuristics is very stupid. It could run ls-tree twice
and try to count intersection.
Giving it wider audience would help it to get improved by
motivated volunteers.
Signed-off-by: Junio C Hamano <junkio@cox.net>
* maint:
Add Documentation/cmd-list.made to .gitignore
git-svn: fix log command to avoid infinite loop on long commit messages
git-svn: dcommit/rebase confused by patches with git-svn-id: lines
git-svn: bail out on incorrect command-line options
This bug has been around since the the conversion to use the
Git.pm library back in October or November. Eventually I'd like
"git rev-list/log" to have the option to not truncate overly
long messages.
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>
When patches are merged from another git-svn managed branch,
they will have the git-svn-id: metadata line in them (generated
by git-format-patch).
When doing rebase or dcommit via git-svn, this would cause
git-svn to find the wrong upstream branch. We now verify
that the commit is consistent with the value in the .rev_db
file.
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>
"git svn log" is the only command that needs the pass-through
option in Getopt::Long; otherwise we will bail out and let the
user know something is wrong.
Also, avoid printing out unaccepted mixed-case options (that
are reserved for the command-line) such as --useSvmProps
in the usage() function.
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Documents the new configuration variables and the variable
substitution mechanism.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
* 'jc/read-tree-df' (early part):
Fix switching to a branch with D/F when current branch has file D.
Fix twoway_merge that passed d/f conflict marker to merged_entry().
Fix read-tree --prefix=dir/.
unpack-trees: get rid of *indpos parameter.
unpack_trees.c: pass unpack_trees_options structure to keep_entry() as well.
add_cache_entry(): removal of file foo does not conflict with foo/bar
Don't include the scheme name in gitcvs.dbdriver, it is
always 'dbi' anyway.
Don't allow ':' in driver names nor ';' in database names for
sanity reasons.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Fix a typo: s/Not/Note/
Some formating fixes: Use ` ` syntax for all filenames and
' ' syntax for all commandline switches.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This merge strategy largely piggy-backs on git-merge-recursive.
When merging trees A and B, if B corresponds to a subtree of A,
B is first adjusted to match the tree structure of A, instead of
reading the trees at the same level. This adjustment is also
done to the common ancestor tree.
If you are pulling updates from git-gui repository into git.git
repository, the root level of the former corresponds to git-gui/
subdirectory of the latter. The tree object of git-gui's toplevel
is wrapped in a fake tree object, whose sole entry has name 'git-gui'
and records object name of the true tree, before being used by
the 3-way merge code.
If you are merging the other way, only the git-gui/ subtree of
git.git is extracted and merged into git-gui's toplevel.
The detection of corresponding subtree is done by comparing the
pathnames and types in the toplevel of the tree.
Heuristics galore! That's the git way ;-).
Signed-off-by: Junio C Hamano <junkio@cox.net>
When pushing into multiple repositories with git push, via
multiple URL in .git/remotes/$shorthand or multiple url
variables in [remote "$shorthand"] section, we used to stop upon
the first failure. Continue the operation and report the
failure at the end.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This came up on #git when somebody was getting 'unable to create
./objects/tmp_oXXXX' but sweared he had write permission to that
directory. It turned out that the repository URL was changed
and he was accessing a repository he does not have a write
permission anymore.
I am not sure how much this would have helped somebody who
believed he was accessing location when the permission of that
location was changed while he was looking the other way, though.
But giving more information on the error path would be better,
and the next change would be helped with this as well.
Signed-off-by: Junio C Hamano <junkio@cox.net>
* jc/index-output:
git-read-tree --index-output=<file>
_GIT_INDEX_OUTPUT: allow plumbing to output to an alternative index file.
Conflicts:
builtin-apply.c
* cc/bisect:
git-bisect: allow bisecting with only one bad commit.
t6030: add a bit more tests to git-bisect
git-bisect: modernization
Documentation: bisect: "start" accepts one bad and many good commits
Bisect: teach "bisect start" to optionally use one bad and many good revs.
* maint:
Documentation: tighten dependency for git.{html,txt}
Makefile: iconv() on Darwin has the old interface
t5300-pack-object.sh: portability issue using /usr/bin/stat
t3200-branch.sh: small language nit
usermanual.txt: some capitalization nits
Make builtin-branch.c handle the git config file
rename_ref(): only print a warning when config-file update fails
Distinguish branches by more than case in tests.
Avoid composing too long "References" header.
cvsimport: Improve formating consistency
cvsimport: Reorder options in documentation for better understanding
cvsimport: Improve usage error reporting
cvsimport: Improve documentation of CVSROOT and CVS module determination
cvsimport: sync usage lines with existing options
Conflicts:
Documentation/Makefile
Every time _any_ documentation page changed, cmds-*.txt files
were regenerated, which caused git.{html,txt} to be remade. Try
not to update cmds-*.txt files if their new contents match the
old ones.
Signed-off-by: Junio C Hamano <junkio@cox.net>
The libiconv on Darwin uses the old iconv() interface (2nd argument is a
const char **, instead of a char **). Add OLD_ICONV to the Darwin
variable definitions to handle this.
Signed-off-by: Arjen Laarhoven <arjen@yaph.org>
Acked-by: Brian Gernhardt <benji@silverinsanity.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
In the test 'compare delta flavors', /usr/bin/stat is used to get file size.
This isn't portable. There already is a dependency on Perl, use its '-s'
operator to get the file size.
Signed-off-by: Arjen Laarhoven <arjen@yaph.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This allows you to say:
git bisect start
git bisect bad $bad
git bisect next
to start bisection without knowing a good commit. This would
have you try a commit that is half-way since the beginning of
the history, which is rather wasteful if you already know a good
commit, but if you don't (or your history is short enough that
you do not care), there is no reason not to allow this.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This moves the knowledge about .git/config usage out of refs.c and into
builtin-branch.c instead, which allows git-branch to update HEAD to point
at the moved branch before attempting to update the config file. It also
allows git-branch to exit with an error code if updating the config file
should fail.
Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
If git_config_rename_section() fails, rename_ref() used to return 1, which
left HEAD pointing to an absent refs/heads file (since the actual renaming
had already occurred).
Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The renaming without config test changed a branch from q to Q, which
fails on non-case sensitive file systems. Change the test to use q
and q2.
Signed-off-by: Junio C Hamano <junkio@cox.net>
The number of characters in a line MUST be no more than 998 characters,
and SHOULD be no more than 78 characters (RFC2822).
It is much safer to fold the header by ourselves.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Use ' ' syntax for all commandline options mentioned in text.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
The current order the options are documented in makes no sense
at all to me. Reorder them so that similar options are grouped
together and also order them somehwhat by importance.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Actually tell the user what he did wrong in case of usage errors
instead of only printing the general usage information.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Document the fact that git-cvsimport tries to find out CVSROOT from
CVS/Root and $ENV{CVSROOT} and CVS_module from CVS/Repository.
Also use ` ` syntax for all filenames for consistency.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Sync both the usage lines in the code and the asciidoc
documentation with the real list of options. While
all options seems to be documented in the asciidoc
document, not all of them were listed in the usage line.
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This slightly modernizes the bisect script to use show-ref/for-each-ref
instead of looking into $GIT_DIR/refs files directly.
Signed-off-by: Junio C Hamano <junkio@cox.net>
