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In want_object_in_pack(), we can exit early from our loop if
neither "local" nor "ignore_pack_keep" are set. If they are,
however, we must examine each pack to see if it has the
object and is non-local or has a ".keep".
It's quite common for there to be no non-local or .keep
packs at all, in which case we know ahead of time that
looking further will be pointless. We can pre-compute this
by simply iterating over the list of packs ahead of time,
and dropping the flags if there are no packs that could
match.
Another similar strategy would be to modify the loop in
want_object_in_pack() to notice that we have already found
the object once, and that we are looping only to check for
"local" and "keep" attributes. If a pack has neither of
those, we can skip the call to find_pack_entry_one(), which
is the expensive part of the loop.
This has two advantages:
- it isn't all-or-nothing; we still get some improvement
when there's a small number of kept or non-local packs,
and a large number of non-kept local packs
- it eliminates any possible race where we add new
non-local or kept packs after our initial scan. In
practice, I don't think this race matters; we already
cache the packed_git information, so somebody who adds a
new pack or .keep file after we've started will not be
noticed at all, unless we happen to need to call
reprepare_packed_git() because a lookup fails.
In other words, we're already racy, and the race is not
a big deal (losing the race means we might include an
object in the pack that would not otherwise be, which is
an acceptable outcome).
However, it also has a disadvantage: we still loop over the
rest of the packs for each object to check their flags. This
is much less expensive than doing the object lookup, but
still not free. So if we wanted to implement that strategy
to cover the non-all-or-nothing cases, we could do so in
addition to this one (so you get the most speedup in the
all-or-nothing case, and the best we can do in the other
cases). But given that the all-or-nothing case is likely the
most common, it is probably not worth the trouble, and we
can revisit this later if evidence points otherwise.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from http://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. The mailing list archives are available at http://news.gmane.org/gmane.comp.version-control.git/, http://marc.info/?l=git and other archival sites.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks