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Each pack has an index for looking up entries in O(log n)
time, but if we have multiple packs, we have to scan through
them linearly. This can produce a measurable overhead for
some operations.
We dealt with this long ago in f7c22cc (always start looking
up objects in the last used pack first, 2007-05-30), which
keeps what is essentially a 1-element most-recently-used
cache. In theory, we should be able to do better by keeping
a similar but longer cache, that is the same length as the
pack-list itself.
Since we now have a convenient generic MRU structure, we can
plug it in and measure. Here are the numbers for running
p5303 against linux.git:
Test HEAD^ HEAD
------------------------------------------------------------------------
5303.3: rev-list (1) 31.56(31.28+0.27) 31.30(31.08+0.20) -0.8%
5303.4: repack (1) 40.62(39.35+2.36) 40.60(39.27+2.44) -0.0%
5303.6: rev-list (50) 31.31(31.06+0.23) 31.23(31.00+0.22) -0.3%
5303.7: repack (50) 58.65(69.12+1.94) 58.27(68.64+2.05) -0.6%
5303.9: rev-list (1000) 38.74(38.40+0.33) 31.87(31.62+0.24) -17.7%
5303.10: repack (1000) 367.20(441.80+4.62) 342.00(414.04+3.72) -6.9%
The main numbers of interest here are the rev-list ones
(since that is exercising the normal object lookup code
path). The single-pack case shouldn't improve at all; the
260ms speedup there is just part of the run-to-run noise
(but it's important to note that we didn't make anything
worse with the overhead of maintaining our cache). In the
50-pack case, we see similar results. There may be a slight
improvement, but it's mostly within the noise.
The 1000-pack case does show a big improvement, though. That
carries over to the repack case, as well. Even though we
haven't touched its pack-search loop yet, it does still do a
lot of normal object lookups (e.g., for the internal
revision walk), and so improves.
As a point of reference, I also ran the 1000-pack test
against a version of HEAD^ with the last_found_pack
optimization disabled. It takes ~60s, so that gives an
indication of how much even the single-element cache is
helping.
For comparison, here's a smaller repository, git.git:
Test HEAD^ HEAD
---------------------------------------------------------------------
5303.3: rev-list (1) 1.56(1.54+0.01) 1.54(1.51+0.02) -1.3%
5303.4: repack (1) 1.84(1.80+0.10) 1.82(1.80+0.09) -1.1%
5303.6: rev-list (50) 1.58(1.55+0.02) 1.59(1.57+0.01) +0.6%
5303.7: repack (50) 2.50(3.18+0.04) 2.50(3.14+0.04) +0.0%
5303.9: rev-list (1000) 2.76(2.71+0.04) 2.24(2.21+0.02) -18.8%
5303.10: repack (1000) 13.21(19.56+0.25) 11.66(18.01+0.21) -11.7%
You can see that the percentage improvement is similar.
That's because the lookup we are optimizing is roughly
O(nr_objects * nr_packs). Since the number of packs is
constant in both tests, we'd expect the improvement to be
linear in the number of objects. But the whole process is
also linear in the number of objects, so the improvement
is a constant factor.
The exact improvement does also depend on the contents of
the packs. In p5303, the extra packs all have 5 first-parent
commits in them, which is a reasonable simulation of a
pushed-to repository. But it also means that only 250
first-parent commits are in those packs (compared to almost
50,000 total in linux.git), and the rest are in the huge
"base" pack. So once we start looking at history in taht big
pack, that's where we'll find most everything, and even the
1-element cache gets close to 100% cache hits. You could
almost certainly show better numbers with a more
pathological case (e.g., distributing the objects more
evenly across the packs). But that's simply not that
realistic a scenario, so it makes more sense to focus on
these numbers.
The implementation itself is a straightforward application
of the MRU code. We provide an MRU-ordered list of packs
that shadows the packed_git list. This is easy to do because
we only create and revise the pack list in one place. The
"reprepare" code path actually drops the whole MRU and
replaces it for simplicity. It would be more efficient to
just add new entries, but there's not much point in
optimizing here; repreparing happens rarely, and only after
doing a lot of other expensive work. The key things to keep
optimized are traversal (which is just a normal linked list,
albeit with one extra level of indirection over the regular
packed_git list), and marking (which is a constant number of
pointer assignments, though slightly more than the old
last_found_pack was; it doesn't seem to create a measurable
slowdown, though).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There are a few places in Git that would benefit from a fast
most-recently-used cache (e.g., the list of packs, which we
search linearly but would like to order based on locality).
This patch introduces a generic list that can be used to
store arbitrary pointers in most-recently-used order.
The implementation is just a doubly-linked list, where
"marking" an item as used moves it to the front of the list.
Insertion and marking are O(1), and iteration is O(n).
There's no lookup support provided; if you need fast
lookups, you are better off with a different data structure
in the first place.
There is also no deletion support. This would not be hard to
do, but it's not necessary for handling pack structs, which
are created and never removed.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The point of this function is to drop an entry from the
"packed_git" cache that points to a file we might be
overwriting, because our contents may not be the same (and
hence the only caller was pack-objects as it moved a
temporary packfile into place).
In older versions of git, this could happen because the
names of packfiles were derived from the set of objects they
contained, not the actual bits on disk. But since 1190a1a
(pack-objects: name pack files after trailer hash,
2013-12-05), the name reflects the actual bits on disk, and
any two packfiles with the same name can be used
interchangeably.
Dropping this function not only saves a few lines of code,
it makes the lifetime of "struct packed_git" much easier to
reason about: namely, we now do not ever free these structs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Git's pack storage does efficient (log n) lookups in a
single packfile's index, but if we have multiple packfiles,
we have to linearly search each for a given object. This
patch introduces some timing tests for cases where we have a
large number of packs, so that we can measure any
improvements we make in the following patches.
The main thing we want to time is object lookup. To do this,
we measure "git rev-list --objects --all", which does a
fairly large number of object lookups (essentially one per
object in the repository).
However, we also measure the time to do a full repack, which
is interesting for two reasons. One is that in addition to
the usual pack lookup, it has its own linear iteration over
the list of packs. And two is that because it it is the tool
one uses to go from an inefficient many-pack situation back
to a single pack, we care about its performance not only at
marginal numbers of packs, but at the extreme cases (e.g.,
if you somehow end up with 5,000 packs, it is the only way
to get back to 1 pack, so we need to make sure it performs
well).
We measure the performance of each command in three
scenarios: 1 pack, 50 packs, and 1,000 packs.
The 1-pack case is a baseline; any optimizations we do to
handle multiple packs cannot possibly perform better than
this.
The 50-pack case is as far as Git should generally allow
your repository to go, if you have auto-gc enabled with the
default settings. So this represents the maximum performance
improvement we would expect under normal circumstances.
The 1,000-pack case is hopefully rare, though I have seen it
in the wild where automatic maintenance was broken for some
time (and the repository continued to receive pushes). This
represents cases where we care less about general
performance, but want to make sure that a full repack
command does not take excessively long.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git p4" used a location outside $GIT_DIR/refs/ to place its
temporary branches, which has been moved to refs/git-p4-tmp/.
* ls/p4-tmp-refs:
git-p4: place temporary refs used for branch import under refs/git-p4-tmp
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One part of "git am" had an oddball helper function that called
stuff from outside "his" as opposed to calling what we have "ours",
which was not gender-neutral and also inconsistent with the rest of
the system where outside stuff is usuall called "theirs" in
contrast to "ours".
* js/am-call-theirs-theirs-in-fallback-3way:
am: counteract gender bias
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General code clean-up around a helper function to write a
single-liner to a file.
* jk/write-file:
branch: use write_file_buf instead of write_file
use write_file_buf where applicable
write_file: add format attribute
write_file: add pointer+len variant
write_file: use xopen
write_file: drop "gently" form
branch: use non-gentle write_file for branch description
am: ignore return value of write_file()
config: fix bogus fd check when setting up default config
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Code clean-up to avoid using a variable string that compilers may
feel untrustable as printf-style format given to write_file()
helper function.
* jk/printf-format:
commit.c: remove print_commit_list()
avoid using sha1_to_hex output as printf format
walker: let walker_say take arbitrary formats
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The .c/.h sources are marked as such in our .gitattributes file so
that "git diff -W" and friends would work better.
* rs/help-c-source-with-gitattributes:
.gitattributes: set file type for C files
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Improve the look of the way "git fetch" reports what happened to
each ref that was fetched.
* nd/fetch-ref-summary:
fetch: reduce duplicate in ref update status lines with placeholder
fetch: align all "remote -> local" output
fetch: change flag code for displaying tag update and deleted ref
fetch: refactor ref update status formatting code
git-fetch.txt: document fetch output
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The test framework learned a new helper test_match_signal to
check an exit code from getting killed by an expected signal.
* jk/test-match-signal:
t/lib-git-daemon: use test_match_signal
test_must_fail: use test_match_signal
t0005: use test_match_signal as appropriate
tests: factor portable signal check out of t0005
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There are certain house-keeping tasks that need to be performed at
the very beginning of any Git program, and programs that are not
built-in commands had to do them exactly the same way as "git"
potty does. It was easy to make mistakes in one-off standalone
programs (like test helpers). A common "main()" function that
calls cmd_main() of individual program has been introduced to
make it harder to make mistakes.
* jk/common-main:
mingw: declare main()'s argv as const
common-main: call git_setup_gettext()
common-main: call restore_sigpipe_to_default()
common-main: call sanitize_stdfds()
common-main: call git_extract_argv0_path()
add an extra level of indirection to main()
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A test that unconditionally used "mktemp" learned that the command
is not necessarily available everywhere.
* ak/lazy-prereq-mktemp:
t7610: test for mktemp before test execution
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"git grep -i" has been taught to fold case in non-ascii locales
correctly.
* nd/icase:
grep.c: reuse "icase" variable
diffcore-pickaxe: support case insensitive match on non-ascii
diffcore-pickaxe: Add regcomp_or_die()
grep/pcre: support utf-8
gettext: add is_utf8_locale()
grep/pcre: prepare locale-dependent tables for icase matching
grep: rewrite an if/else condition to avoid duplicate expression
grep/icase: avoid kwsset when -F is specified
grep/icase: avoid kwsset on literal non-ascii strings
test-regex: expose full regcomp() to the command line
test-regex: isolate the bug test code
grep: break down an "if" stmt in preparation for next changes
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Conversion from unsigned char sha1[20] to struct object_id
continues.
* bc/cocci:
diff: convert prep_temp_blob() to struct object_id
merge-recursive: convert merge_recursive_generic() to object_id
merge-recursive: convert leaf functions to use struct object_id
merge-recursive: convert struct merge_file_info to object_id
merge-recursive: convert struct stage_data to use object_id
diff: rename struct diff_filespec's sha1_valid member
diff: convert struct diff_filespec to struct object_id
coccinelle: apply object_id Coccinelle transformations
coccinelle: convert hashcpy() with null_sha1 to hashclr()
contrib/coccinelle: add basic Coccinelle transforms
hex: add oid_to_hex_r()
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The commands in the "log/diff" family have had an FILE* pointer in the
data structure they pass around for a long time, but some codepaths
used to always write to the standard output. As a preparatory step
to make "git format-patch" available to the internal callers, these
codepaths have been updated to consistently write into that FILE*
instead.
* js/log-to-diffopt-file:
mingw: fix the shortlog --output=<file> test
diff: do not color output when --color=auto and --output=<file> is given
t4211: ensure that log respects --output=<file>
shortlog: respect the --output=<file> setting
format-patch: use stdout directly
format-patch: avoid freopen()
format-patch: explicitly switch off color when writing to files
shortlog: support outputting to streams other than stdout
graph: respect the diffopt.file setting
line-log: respect diffopt's configured output file stream
log-tree: respect diffopt's configured output file stream
log: prepare log/log-tree to reuse the diffopt.close_file attribute
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Fix recently introduced codepaths that are involved in parallel
submodule operations, which gave up on reading too early, and
could have wasted CPU while attempting to write under a corner
case condition.
* sb/submodule-parallel-fetch:
hoist out handle_nonblock function for xread and xwrite
xwrite: poll on non-blocking FDs
xread: retry after poll on EAGAIN/EWOULDBLOCK
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Code simplification.
* lf/recv-sideband-cleanup:
sideband.c: small optimization of strbuf usage
sideband.c: refactor recv_sideband()
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"git blame -M" missed a single line that was moved within the file.
* dk/blame-move-no-reason-for-1-line-context:
blame: require 0 context lines while finding moved lines with -M
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A new configuration variable core.sshCommand has been added to
specify what value for GIT_SSH_COMMAND to use per repository.
* nd/connect-ssh-command-config:
connect: read $GIT_SSH_COMMAND from config file
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As we are not yet moving everything to size_t but still using ulong
internally when talking about the size of object, platforms with
32-bit long will not be able to produce tar archive with 4GB+ file,
and cannot grok 077777777777UL as a constant. Disable the extended
header feature and do not test it on them.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* maint:
Git 2.9.2
t0006: skip "far in the future" test when unsigned long is not long enough
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Skip tests that are unrunnable on platforms without 64-bit long
to avoid unnecessary test failures.
* jk/tzoffset-fix:
t0006: skip "far in the future" test when unsigned long is not long enough
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Git's source code refers to timestamps as unsigned longs. On 32-bit
platforms, as well as on Windows, unsigned long is not large enough
to capture dates that are "absurdly far in the future".
While we can fix this issue properly by replacing unsigned long with
a larger type, we want to be a bit more conservative and just skip
those tests on the maint track.
Signed-off-by: Jeff King <peff@peff.net>
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A hot-fix to make a test working in mingw again.
* jk/upload-pack-hook:
mingw: fix regression in t1308-config-set
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When we tried to fix in 58461bd (t1308: do not get fooled by symbolic
links to the source tree, 2016-06-02) an obscure case where the user
cd's into Git's source code via a symbolic link, a regression was
introduced that affects all test runs on Windows.
The original patch introducing the test case in question was careful to
use `$(pwd)` instead of `$PWD`.
This was done to account for the fact that Git's test suite uses shell
scripting even on Windows, where the shell's Unix-y paths are
incompatible with the main Git executable's idea of paths: it only
accepts Windows paths.
It is an awkward but necessary thing, then, to use `$(pwd)` (which gives
us a Windows path) when interacting with the Git executable and `$PWD`
(which gives the shell's idea of the current working directory in Unix-y
form) for shell scripts, including the test suite itself.
Obviously this broke the use case of the Git maintainer when changing
the working directory into Git's source code directory via a symlink,
i.e. when `$(pwd)` does not agree with `$PWD`.
However, we must not fix that use case at the expense of regressing
another use case.
Let's special-case Windows here, even if it is ugly, for lack of a more
elegant solution.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git archive" learned to handle files that are larger than 8GB and
commits far in the future than expressible by the traditional US-TAR
format.
* jk/big-and-future-archive-tar:
archive-tar: drop return value
archive-tar: write extended headers for far-future mtime
archive-tar: write extended headers for file sizes >= 8GB
t5000: test tar files that overflow ustar headers
t9300: factor out portable "head -c" replacement
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Git does not know what the contents in the index should be for a
path added with "git add -N" yet, so "git grep --cached" should not
show hits (or show lack of hits, with -L) in such a path, but that
logic does not apply to "git grep", i.e. searching in the working
tree files. But we did so by mistake, which has been corrected.
* nd/ita-cleanup:
grep: fix grepping for "intent to add" files
t7810-grep.sh: fix a whitespace inconsistency
t7810-grep.sh: fix duplicated test name
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"git rebase -i --autostash" did not restore the auto-stashed change
when the operation was aborted.
* ps/rebase-i-auto-unstash-upon-abort:
rebase -i: restore autostash on abort
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Grammofix.
* js/t3404-grammo-fix:
t3404: fix a grammo (commands are ran -> commands are run)
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"git commit --amend --allow-empty-message -S" for a commit without
any message body could have misidentified where the header of the
commit object ends.
* js/sign-empty-commit-fix:
commit -S: avoid invalid pointer with empty message
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More mark-up updates to typeset strings that are expected to
literally typed by the end user in fixed-width font.
* mm/doc-tt:
doc: typeset HEAD and variants as literal
CodingGuidelines: formatting HEAD in documentation
doc: typeset long options with argument as literal
doc: typeset '--' as literal
doc: typeset long command-line options as literal
doc: typeset short command-line options as literal
Documentation/git-mv.txt: fix whitespace indentation
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Add a test to specify the desired behaviour that currently is not
available in "git rebase -Xsubtree=...".
* dg/subtree-rebase-test:
contrib/subtree: Add a test for subtree rebase that loses commits
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Typofix in a doc.
* nd/doc-new-command:
new-command.txt: correct the command description file
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"gc.autoPackLimit" when set to 1 should not trigger a repacking
when there is only one pack, but the code counted poorly and did
so.
* ew/gc-auto-pack-limit-fix:
gc: fix off-by-one error with gc.autoPackLimit
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Grammofix.
* ah/unpack-trees-advice-messages:
unpack-trees: fix English grammar in do-this-before-that messages
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More markings of messages for i18n, with updates to various tests
to pass GETTEXT_POISON tests.
One patch from the original submission dropped due to conflicts
with jk/upload-pack-hook, which is still in flux.
* va/i18n-even-more: (38 commits)
t5541: become resilient to GETTEXT_POISON
i18n: branch: mark comment when editing branch description for translation
i18n: unmark die messages for translation
i18n: submodule: escape shell variables inside eval_gettext
i18n: submodule: join strings marked for translation
i18n: init-db: join message pieces
i18n: remote: allow translations to reorder message
i18n: remote: mark URL fallback text for translation
i18n: standardise messages
i18n: sequencer: add period to error message
i18n: merge: change command option help to lowercase
i18n: merge: mark messages for translation
i18n: notes: mark options for translation
i18n: notes: mark strings for translation
i18n: transport-helper.c: change N_() call to _()
i18n: bisect: mark strings for translation
t5523: use test_i18ngrep for negation
t4153: fix negated test_i18ngrep call
t9003: become resilient to GETTEXT_POISON
tests: unpack-trees: update to use test_i18n* functions
...
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Adjust t4201 to pass on Windows; a couple of test cases need to be
skipped on Windows which leads to a different shortlog than on Linux.
Let's just fix that by limiting the shortlog's commit range to traverse
only one commit: that guarantees that it does not matter how many test
cases were skipped.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* maint:
Git 2.9.1
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Portability fix for Windows.
* jc/t2300-setup:
t2300: "git --exec-path" is not usable in $PATH on Windows as-is
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Test clean-up.
* cb/t7810-test-label-fix:
t7810: fix duplicated test title
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Test clean-up.
* sb/t5614-modernize:
t5614: don't use subshells
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The top level documentation "git help git" still pointed at the
documentation set hosted at now-defunct google-code repository.
Update it to point to https://git.github.io/htmldocs/git.html
instead.
* jn/preformatted-doc-url:
doc: git-htmldocs.googlecode.com is no more
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A bug, which caused "git p4" while running under verbose mode to
report paths that are omitted due to branch prefix incorrectly, has
been fixed; the command said "Ignoring file outside of prefix" for
paths that are _inside_.
* ao/p4-has-branch-prefix-fix:
git-p4: correct hasBranchPrefix verbose output
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t/perf needs /usr/bin/time with GNU extension; the invocation of it
is updated to "gtime" on Darwin.
* js/perf-on-apple:
perf: accommodate for MacOSX
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One among four invocations of readlink(1) in our test suite has
been rewritten so that the test can run on systems without the
command (others are in valgrind test framework and t9802).
* ak/t7800-wo-readlink:
t7800: readlink may not be available
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Jeff King
Junio C Hamano
Johannes Schindelin