The lookup_object function is backed by a hash table of all
objects we have seen in the program. We manage collisions
with a linear walk over the colliding entries, checking each
with hashcmp(). The main cost of lookup is in these
hashcmp() calls; finding our item in the first slot is
cheaper than finding it in the second slot, which is cheaper
than the third, and so on.
If we assume that there is some locality to the object
lookups (e.g., if X and Y collide, and we have just looked
up X, the next lookup is more likely to be for X than for
Y), then we can improve our average lookup speed by checking
X before Y.
This patch does so by swapping a found item to the front of
the collision chain. The p0001 perf test reveals that this
does indeed exploit locality in the case of "rev-list --all
--objects":
Test origin this tree
-------------------------------------------------------------------------
0001.1: rev-list --all 0.40(0.38+0.02) 0.40(0.36+0.03) +0.0%
0001.2: rev-list --all --objects 2.24(2.17+0.05) 1.86(1.79+0.05) -17.0%
This is not surprising, as the full object traversal will
hit the same tree entries over and over (e.g., for every
commit that doesn't change "Documentation/", we will have to
look up the same sha1 just to find out that we already
processed it).
The reason why this technique works (and does not violate
any properties of the hash table) is subtle and bears some
explanation. Let's imagine we get a lookup for sha1 `X`, and
it hashes to bucket `i` in our table. That stretch of the
table may look like:
index | i-1 | i | i+1 | i+2 |
-----------------------------------
entry ... | A | B | C | X | ...
-----------------------------------
We start our probe at i, see that B does not match, nor does
C, and finally find X. There may be multiple C's in the
middle, but we know that there are no empty slots (or else
we would not find X at all).
We do not know the original index of B; it may be `i`, or it
may be less than i (e.g., if it were `i-1`, it would collide
with A and spill over into the `i` bucket). So it is
acceptable for us to move it to the right of a contiguous
stretch of entries (because we will find it from a linear
walk starting anywhere at `i` or before), but never to the
left (if we moved it to `i-1`, we would miss it when
starting our walk at `i`).
We do know the original index of X; it is `i`, so it is safe
to place it anywhere in the contiguous stretch between `i`
and where we found it (`i+2` in the this case).
This patch does a pure swap; after finding X in the
situation above, we would end with:
index | i-1 | i | i+1 | i+2 |
-----------------------------------
entry ... | A | X | C | B | ...
-----------------------------------
We could instead bump X into the `i` slot, and then shift
the whole contiguous chain down by one, resulting in:
index | i-1 | i | i+1 | i+2 |
-----------------------------------
entry ... | A | X | B | C | ...
-----------------------------------
That puts our chain in true most-recently-used order.
However, experiments show that it is not any faster (and in
fact, is slightly slower due to the extra manipulation).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We earlier removed a link to list of contributors that pointed to a
defunct page; let's use a working one from Ohloh.net to replace it
instead.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* sl/maint-git-svn-docs:
git-svn: Note about tags.
git-svn: Expand documentation for --follow-parent
git-svn: Recommend use of structure options.
git-svn: Document branches with at-sign(@).
Document that 'git svn' will import SVN tags as branches.
Signed-off-by: Sebastian Leske <sebastian.leske@sleske.name>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Describe what the option --follow-parent does, and what happens if it is
set or unset.
Signed-off-by: Sebastian Leske <sebastian.leske@sleske.name>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Document that when using git svn, one should usually either use the
directory structure options to import branches as branches, or only
import one subdirectory. The default behaviour of cloning all branches
and tags as subdirectories in the working copy is usually not what the
user wants.
Signed-off-by: Sebastian Leske <sebastian.leske@sleske.name>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
git svn sometimes creates branches with an at-sign in the name
(branchname@revision). These branches confuse many users and it is a FAQ
why they are created. Document when git svn creates them.
Signed-off-by: Sebastian Leske <sebastian.leske@sleske.name>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In the distant past, the order things were documented was
'Invocation', 'Commands', 'Capabilities', ...
Then it was decided that before giving a list of Commands, there
should be an overall description of the 'Input format', which was
a wise decision. However, this description was put as the very
first thing, with the rationale that any implementor would want
to know that first.
However, it seems an implementor would actually first need to
know how the remote helper will be invoked, so moving
'Invocation' to the front again seems logical. Moreover, we now
don't switch from discussing the input format to the invocation
style and then back to input related stuff.
Signed-off-by: Max Horn <max@quendi.de>
Acked-by: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
19299a8 (Documentation: Move diff.<driver>.* from config.txt to
diff-config.txt, 2011-04-07) moved the diff configuration options to
diff-config.txt, but forgot about diff.wordRegex, which was left
behind in config.txt. Fix this.
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* jk/mailmap-cleanup:
contrib: update stats/mailmap script
.mailmap: normalize emails for Linus Torvalds
.mailmap: normalize emails for Jeff King
.mailmap: fix broken entry for Martin Langhoff
.mailmap: match up some obvious names/emails
* ta/doc-cleanup:
Documentation: build html for all files in technical and howto
Documentation/howto: convert plain text files to asciidoc
Documentation/technical: convert plain text files to asciidoc
Change headline of technical/send-pack-pipeline.txt to not confuse its content with content from git-send-pack.txt
Shorten two over-long lines in git-bisect-lk2009.txt by abbreviating some sha1
Split over-long synopsis in git-fetch-pack.txt into several lines
Howto documents in howto-index.txt were listed in a rather
random order. So better sort them.
Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As it was not a common operation, it was described as if it is a
side note for the more common two-commit variant, but this mode
behaves very differently, e.g. it does not make any sense to ask
recursive behaviour, or give the command a pathspec.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These tests themselves are properly protected by the GPG
prerequisite, but one of the set-up steps outside the
test_expect_success block unconditionally assumed that there is a
gpghome/ directory, which is not true if GPG is not being used.
It may be a good idea to move the whole set-up steps in the test but
that is a follow-up topic.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Document the behavior implemented in 70c9ac2 (DWIM "git checkout
frotz" to "git checkout -b frotz origin/frotz").
Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The forms of checkout that do not take a path are lumped together in
the DESCRIPTION section, but the description for this group is
dominated by explanation of the -b|-B form.
Split these apart for more clarity.
Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git log -p -S<string>" now looks for the <string> after applying
the textconv filter (if defined); earlier it inspected the contents
of the blobs without filtering.
The "Try to be nice to older C compilers" text is clearly a guideline
to be borne in mind whilst coding rather than when submitting patches.
Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Conscientious newcomers to git development will read SubmittingPatches
and CodingGuidelines, but could easily miss the convention of
prefixing commit messages with a single word identifying the file
or area the commit touches.
Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Email addresses in documentation are converted into mailto: hyperlinks
in the HTML output and footnotes in man pages. This isn't desirable for
cases where the address is used as an example and is not valid.
Particularly annoying is the example "jane@laptop.(none)" which appears
in git-shortlog(1) as "jane@laptop[1].(none)", with note 1 saying:
1. jane@laptop
mailto:jane@laptop
Fix this by escaping these email addresses with a leading backslash, to
prevent Asciidoc expanding them as inline macros.
In the case of mailmap.txt, render the address monospaced so that it
matches the block examples surrounding that paragraph.
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The audience of this introductory document does not have to know nor
interact with the maintainer, so drop the mention of him. Other
documents such as SubmittingPatches may be a more suitable place to
have it.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
And this is clearly stressed by Linus in the COPYING file. So make it
clear in the README as well, to avoid possible misunderstandings.
Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Explain that --tags is just like another explicit refspec on the
command line and as such overrides the default refspecs configured
via the remote.$name.fetch variable.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Currently it gets the size of an otherwise unrelated, unused variable
instead of the expected struct size.
Signed-off-by: Matthew Daley <mattjd@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Unlike other environment variables (e.g. GIT_WORK_TREE, GIT_NAMESPACE),
the Documentation/git.txt file did not mention that the GIT_DIR
environment variable can also be set using the --git-dir command line
option.
Signed-off-by: Manlio Perillo <manlio.perillo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A cache-tree entry with a negative entry count is considered invalid
by the current Git; it records that we do not know the object name
of a tree that would result by writing the directory covered by the
cache-tree as a tree object.
Clarify that any entry with a negative entry count is invalid, but
the implementations must write -1 there. This way, we can later
decide to allow writers to use negative values other than -1 to
encode optional information on such invalidated entries without
harming interoperability; we do not know what will be encoded and
how, so we keep these other negative values as reserved for now.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This version changes quite a few things:
1. The original parsed the mailmap file itself, and it did
it wrong (it did not understand entries with an extra
email key).
Instead, this version uses git's "%aE" and "%aN"
formats to have git perform the mapping, meaning we do
not have to read .mailmap at all, but still operate on
the current state that git sees (and it also works
properly from subdirs).
2. The original would find multiple names for an email,
but not the other way around.
This version can do either or both. If we find multiple
emails for a name, the resolution is less obvious than
the other way around. However, it can still be a
starting point for a human to investigate.
3. The original would order only by count, not by recency.
This version can do either. Combined with showing the
counts, it can be easier to decide how to resolve.
4. This version shows similar entries in a blank-delimited
stanza, which makes it more clear which options you are
picking from.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Linus used a lot of different per-machine email addresses in
the early days. This means that "git shortlog -nse" does not
aggregate his counts, and he is listed well below where he
should be (8th instead of 3rd).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
I never meant anything special by using my @github.com
address; it is merely a mistake that it has sometimes bled
through to patches.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit adc3192 (Martin Langhoff has a new e-mail address,
2010-10-05) added a mailmap entry, but forgot that both the
old and new email addresses need to appear for one to be
mapped to the other (i.e., we do not key mailmap emails by
name).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This patch updates git's .mailmap in cases where multiple
names are matched to a single email. The "master" name for
each email was chosen by:
1. If the only difference is in the presence or absence
of accented characters, the accented form is chosen
(under the assumption that it is the natural spelling,
and accents are sometimes stripped in email).
2. Otherwise, the most commonly used name is chosen.
3. If all names are equally common, the most recently used name is
chosen.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
GIT_PS1_DESCRIBE_STYLE was introduced in v1.6.3.2~35. Document it in the
header comments.
Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The linked page has not been showing the promised "more complete
list" for more than 6 months by now, and nobody has resurrected
the list there nor elsewhere since then.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
