Add a warning about missing thread support when grep.threads or
--threads is set to a non 0 (default) or 1 (no parallelism) value
under NO_PTHREADS=YesPlease.
This is for consistency with the index-pack & pack-objects commands,
which also take a --threads option & are configurable via
pack.threads, and have long warned about the same under
NO_PTHREADS=YesPlease.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fix a buggy warning about threads under NO_PTHREADS=YesPlease. Due to
re-using the delta_search_threads variable for both the state of the
"pack.threads" config & the --threads option, setting "pack.threads"
but not supplying --threads would trigger the warning for both
"pack.threads" & --threads.
Solve this bug by resetting the delta_search_threads variable in
git_pack_config(), it might then be set by --threads again and be
subsequently warned about, as the test I'm changing here asserts.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a test for the warning that's emitted when --threads or
pack.threads is provided under NO_PTHREADS=YesPlease. This uses the
new PTHREADS prerequisite.
The assertion for C_LOCALE_OUTPUT in the latter test is currently
redundant, since unlike index-pack the pack-objects warnings aren't
i18n'd. However they might be changed to be i18n'd in the future, and
there's no harm in future-proofing the test.
There's an existing bug in the implementation of pack-objects which
this test currently tests for as-is. Details about the bug & the fix
are included in a follow-up change.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a PTHREADS prerequisite which is false when git is compiled with
NO_PTHREADS=YesPlease.
There's lots of custom code that runs when threading isn't available,
but before this prerequisite there was no way to test it.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move the is_fixed() function which are currently only used in
compile_regexp() earlier so it can be used in the PCRE family of
functions in a later change.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change the internal PCRE variable & function names to have a "1"
suffix. This is for preparation for libpcre2 support, where having
non-versioned names would be confusing.
An earlier change in this series ("grep: change the internal PCRE
macro names to be PCRE1", 2017-04-07) elaborates on the motivations
behind this change.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change the internal USE_LIBPCRE define, & build options flag to use a
naming convention ending in PCRE1, without changing the long-standing
USE_LIBPCRE Makefile flag which enables this code.
This is for preparation for libpcre2 support where having things like
USE_LIBPCRE and USE_LIBPCRE2 in any more places than we absolutely
need to for backwards compatibility with old Makefile arguments would
be confusing.
In some ways it would be better to change everything that now uses
USE_LIBPCRE to use USE_LIBPCRE1, and to make specifying
USE_LIBPCRE (or --with-pcre) an error. This would impose a one-time
burden on packagers of git to s/USE_LIBPCRE/USE_LIBPCRE1/ in their
build scripts.
However I'd like to leave the door open to making
USE_LIBPCRE=YesPlease eventually mean USE_LIBPCRE2=YesPlease,
i.e. once PCRE v2 is ubiquitous enough that it makes sense to make it
the default.
This code and the USE_LIBPCRE Makefile argument was added in commit
63e7e9d8b6 ("git-grep: Learn PCRE", 2011-05-09). At the time there was
no indication that the PCRE project would release an entirely new &
incompatible API around 3 years later.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Factor the test for \0 in grep patterns into a function. Since commit
9eceddeec6 ("Use kwset in grep", 2011-08-21) any pattern containing a
\0 is considered fixed as regcomp() can't handle it.
This change makes later changes that make use of either has_null() or
is_fixed() (but not both) smaller.
While I'm at it make the comment conform to the style guide, i.e. add
an opening "/*\n".
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Remove redundant assignments to the "regflags" variable. This variable
is only used set under GREP_PATTERN_TYPE_ERE, so there's no need to
un-set it under GREP_PATTERN_TYPE_{FIXED,BRE,PCRE}.
Back in 5010cb5fcc[1], we did do "opt.regflags &= ~REG_EXTENDED" upon
seeing "-G" on the command line and flipped the bit on upon seeing
"-E", but I think that was perfectly sensible and it would have been a
bug if we didn't. They were part of the command line parsing that
could have seen "-E" on the command line earlier.
When cca2c172 ("git-grep: do not die upon -F/-P when
grep.extendedRegexp is set.", 2011-05-09) switched the command line
parsing to "read into a 'tentatively this is what we saw the last'
variable and then finally commit just once", we didn't touch
opt.regflags for PCRE and FIXED, but we still had to flip regflags
between BRE and ERE, because parsing of grep.extendedregexp
configuration variable directly touched opt.regflags back then, which
was done by b22520a3 ("grep: allow -E and -n to be turned on by
default via configuration", 2011-03-30).
When 84befcd0 ("grep: add a grep.patternType configuration setting",
2012-08-03) introduced extended_regexp_option field, we stopped
flipping regflags while reading the configuration, and that was when
we should have noticed and stopped dropping REG_EXTENDED bit in the
"now we can commit what type to use" helper function.
There is no reason to do this anymore, so stop doing it, more to
reduce "wait this is used under fixed/BRE/PCRE how?" confusion when
reading the code, than to to save ourselves trivial CPU cycles by
removing one assignment.
1. "built-in "git grep"", 2006-04-30.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a die(...) to a default case for the switch statement selecting
between grep pattern types under --recurse-submodules.
Normally this would be caught by -Wswitch, but the grep_pattern_type
type is converted to int by going through parse_options(). Changing
the argument type passed to compile_submodule_options() won't work,
the value will just get coerced. The -Wswitch-default warning will
warn about it, but that produces a lot of noise across the codebase,
this potential issue would be drowned in that noise.
Thus catching this at runtime is the least bad option. This won't ever
trigger in practice, but if a new pattern type were to be added this
catches an otherwise silent bug during development.
See commit 0281e487fd ("grep: optionally recurse into submodules",
2016-12-16) for the initial addition of this code.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a performance comparison test of grep regex engines given fixed
strings.
The current logic in compile_regexp() ignores the engine parameter and
uses kwset() to search for these, so this test shows no difference
between engines right now:
$ GIT_PERF_REPEAT_COUNT=10 GIT_PERF_LARGE_REPO=~/g/linux ./run p7821-grep-engines-fixed.sh
[...]
Test this tree
------------------------------------------------
7821.1: fixed grep int 0.56(1.67+0.68)
7821.2: basic grep int 0.57(1.70+0.57)
7821.3: extended grep int 0.59(1.76+0.51)
7821.4: perl grep int 1.08(1.71+0.55)
7821.6: fixed grep uncommon 0.23(0.55+0.50)
7821.7: basic grep uncommon 0.24(0.55+0.50)
7821.8: extended grep uncommon 0.26(0.55+0.52)
7821.9: perl grep uncommon 0.24(0.58+0.47)
7821.11: fixed grep æ 0.36(1.30+0.42)
7821.12: basic grep æ 0.36(1.32+0.40)
7821.13: extended grep æ 0.38(1.30+0.42)
7821.14: perl grep æ 0.35(1.24+0.48)
Only when run with -i via GIT_PERF_7821_GREP_OPTS=' -i' do we avoid
avoid going through the same kwset.[ch] codepath, see the "Even when
-F..." comment in grep.c. This only kicks for the non-ASCII case:
$ GIT_PERF_REPEAT_COUNT=10 GIT_PERF_LARGE_REPO=~/g/linux GIT_PERF_7821_GREP_OPTS=' -i' ./run p7821-grep-engines-fixed.sh
[...]
Test this tree
---------------------------------------------------
7821.1: fixed grep -i int 0.62(2.10+0.57)
7821.2: basic grep -i int 0.68(1.90+0.61)
7821.3: extended grep -i int 0.78(1.94+0.57)
7821.4: perl grep -i int 0.98(1.78+0.74)
7821.6: fixed grep -i uncommon 0.24(0.44+0.64)
7821.7: basic grep -i uncommon 0.25(0.56+0.54)
7821.8: extended grep -i uncommon 0.27(0.62+0.45)
7821.9: perl grep -i uncommon 0.24(0.59+0.49)
7821.11: fixed grep -i æ 0.30(0.96+0.39)
7821.12: basic grep -i æ 0.27(0.92+0.44)
7821.13: extended grep -i æ 0.28(0.90+0.46)
7821.14: perl grep -i æ 0.28(0.74+0.49)
I'm planning to change how fixed-string searching happens. This test
gives a baseline for comparing performance before & after any such
change.
See commit ("perf: add a comparison test of grep regex engines",
2017-04-19) for details on the machine the above test run was executed
on.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a very basic performance comparison test comparing the POSIX
basic, extended and perl engines.
In theory the "basic" and "extended" engines should be implemented
using the same underlying code with a slightly different pattern
parser, but some implementations may not do this. Jump through some
slight hoops to test both, which is worthwhile since "basic" is the
default.
Running this on an i7 3.4GHz Linux 4.9.0-2 Debian testing against a
checkout of linux.git & latest upstream PCRE, both PCRE and git
compiled with -O3 using gcc 7.1.1:
$ GIT_PERF_REPEAT_COUNT=10 GIT_PERF_LARGE_REPO=~/g/linux ./run p7820-grep-engines.sh
[...]
Test this tree
---------------------------------------------------------------
7820.1: basic grep 'how.to' 0.34(1.24+0.53)
7820.2: extended grep 'how.to' 0.33(1.23+0.45)
7820.3: perl grep 'how.to' 0.31(1.05+0.56)
7820.5: basic grep '^how to' 0.32(1.24+0.42)
7820.6: extended grep '^how to' 0.33(1.20+0.44)
7820.7: perl grep '^how to' 0.57(2.67+0.42)
7820.9: basic grep '[how] to' 0.51(2.16+0.45)
7820.10: extended grep '[how] to' 0.49(2.20+0.43)
7820.11: perl grep '[how] to' 0.56(2.60+0.43)
7820.13: basic grep '\(e.t[^ ]*\|v.ry\) rare' 0.66(3.25+0.40)
7820.14: extended grep '(e.t[^ ]*|v.ry) rare' 0.65(3.19+0.46)
7820.15: perl grep '(e.t[^ ]*|v.ry) rare' 1.05(5.74+0.34)
7820.17: basic grep 'm\(ú\|u\)lt.b\(æ\|y\)te' 0.34(1.28+0.47)
7820.18: extended grep 'm(ú|u)lt.b(æ|y)te' 0.34(1.38+0.38)
7820.19: perl grep 'm(ú|u)lt.b(æ|y)te' 0.39(1.56+0.44)
Options can also be passed to git-grep via the GIT_PERF_7820_GREP_OPTS
environment variable. There are various modes such as "-v" that have
very different performance profiles, but handling the combinatorial
explosion of testing all those options would make this script much
more complex and harder to maintain. Instead just add the ability to
do one-shot runs with arbitrary options, e.g.:
$ GIT_PERF_REPEAT_COUNT=10 GIT_PERF_LARGE_REPO=~/g/linux GIT_PERF_7820_GREP_OPTS=" -i" ./run p7820-grep-engines.sh
[...]
Test this tree
------------------------------------------------------------------
7820.1: basic grep -i 'how.to' 0.49(1.72+0.38)
7820.2: extended grep -i 'how.to' 0.46(1.64+0.42)
7820.3: perl grep -i 'how.to' 0.44(1.45+0.45)
7820.5: basic grep -i '^how to' 0.47(1.76+0.38)
7820.6: extended grep -i '^how to' 0.47(1.70+0.42)
7820.7: perl grep -i '^how to' 0.65(2.72+0.37)
7820.9: basic grep -i '[how] to' 0.86(3.64+0.42)
7820.10: extended grep -i '[how] to' 0.84(3.62+0.46)
7820.11: perl grep -i '[how] to' 0.73(3.06+0.39)
7820.13: basic grep -i '\(e.t[^ ]*\|v.ry\) rare' 1.63(8.13+0.36)
7820.14: extended grep -i '(e.t[^ ]*|v.ry) rare' 1.64(8.01+0.44)
7820.15: perl grep -i '(e.t[^ ]*|v.ry) rare' 1.44(6.88+0.44)
7820.17: basic grep -i 'm\(ú\|u\)lt.b\(æ\|y\)te' 0.66(2.67+0.44)
7820.18: extended grep -i 'm(ú|u)lt.b(æ|y)te' 0.66(2.67+0.43)
7820.19: perl grep -i 'm(ú|u)lt.b(æ|y)te' 0.59(2.31+0.37)
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Amend the t/perf/run output so that in addition to the "Running N
tests" heading currently being emitted, it also emits "Unpacking $rev"
and "Building $rev" when setting up the build/$rev directory & when
building it, respectively.
This makes it easier to see what's going on and what revision is being
tested as the output scrolls by.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a git GIT_PERF_MAKE_COMMAND variable to compliment the existing
GIT_PERF_MAKE_OPTS facility. This allows specifying an arbitrary shell
command to execute instead of 'make'.
This is useful e.g. in cases where the name, semantics or defaults of
a Makefile flag have changed over time. It can even be used to change
the contents of the tree, useful for monkeypatching ancient versions
of git to get them to build.
This opens Pandora's box in some ways, it's now possible to
"jailbreak" the perf environment and e.g. modify the source tree via
this arbitrary instead of just issuing a custom "make" command, such a
command has to be re-entrant in the sense that subsequent perf runs
will re-use the possibly modified tree.
It would be pointless to try to mitigate or work around that caveat in
a tool purely aimed at Git developers, so this change makes no attempt
to do so.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Address a big blind spot in the tests for patterns containing \0. The
is_fixed() function considers any string that contains \0 fixed, even
if it contains regular expression metacharacters, those patterns are
currently matched with kwset.
Before this change removing that memchr(s, 0, len) check from
is_fixed() wouldn't change the result of any of the tests, since
regcomp() will happily match the part before the \0.
The kwset path is dependent on whether the the -i flag is on, and
whether the pattern has any non-ASCII characters, but none of this was
tested for.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add setup code needed for testing regexes that contain both binary
data and regex metacharacters.
The POSIX regcomp() function inherently can't support that, because it
takes a \0-delimited char *, but other regex engines APIs like PCRE v2
take a pattern/length pair, and are thus able to handle \0s in
patterns as well as any other character.
When kwset was imported in commit 9eceddeec6 ("Use kwset in grep",
2011-08-21) this limitation was fixed, but at the expense of
introducing the undocumented limitation that any pattern containing \0
implicitly becomes a fixed match (equivalent to -F having been
provided).
That's not something we'd like to keep in the future. The inability to
match patterns containing \0 is a leaky implementation detail.
So add tests as a first step towards changing that. In order to test
that \0-patterns can properly match as regexes the test string needs
to have some regex metacharacters in it.
There were other blind spots in the tests. The code around kwset
specially handles case-insensitive & non-ASCII data, but there were no
tests for this.
Fix all of that by amending the text being matched to contain both
regex metacharacters & non-ASCII data.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a helper function to make the tests which check for patterns with
\0 in them more succinct. Right now this isn't a big win, but
subsequent commits will add a lot more of these tests.
The helper is based on the match() function in t3070-wildmatch.sh.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add testing for grep pattern types being correctly passed to
submodules. The pattern "(.|.)[\d]" matches differently under
fixed (not at all), and then matches different lines under
basic/extended & perl regular expressions, so this change asserts that
the pattern type is passed along correctly.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Amend the submodule recursion test to prepare it for subsequent tests
of whether it passes along the grep.patternType to the submodule
greps.
This is the result of searching & replacing:
foobar -> (1|2)d(3|4)
foo -> (1|2)
bar -> (3|4)
Currently there's no tests for whether e.g. -P or -E is correctly
passed along, tests for that will be added in a follow-up change, but
first add content to the tests which will match differently under
different regex engines.
Reuse the pattern established in an earlier commit of mine in this
series ("log: add exhaustive tests for pattern style options &
config", 2017-04-07). The pattern "(.|.)[\d]" will match this content
differently under fixed/basic/extended & perl.
This test code was originally added in commit 0281e487fd ("grep:
optionally recurse into submodules", 2016-12-16).
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add tests for --threads=N being supplied on the command-line, or when
grep.threads=N being supplied in the configuration.
When the threading support was made run-time configurable in commit
89f09dd34e ("grep: add --threads=<num> option and grep.threads
configuration", 2015-12-15) no tests were added for it.
In developing a change to the grep code I was able to make
'--threads=1 <pat>` segfault, while the test suite still passed. This
change fixes that blind spot in the tests.
In addition to asserting that asking for N threads shouldn't segfault,
test that the grep output given any N is the same.
The choice to test only 1..10 as opposed to 1..8 or 1..16 or whatever
is arbitrary. Testing 1..1024 works locally for me (but gets
noticeably slower as more threads are spawned). Given the structure of
the code there's no reason to test an arbitrary number of threads,
only 0, 1 and >=2 are special modes of operation.
A later patch introduces a PTHREADS test prerequisite which is true
under NO_PTHREADS=UnfortunatelyYes, but even under NO_PTHREADS it's
fine to test --threads=N, we'll just ignore it and not use
threading. So these tests also make sense under that mode to assert
that --threads=N without pthreads still returns expected results.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change a non-ASCII case-insensitive test case to stop using --debug,
and instead simply test for the expected results.
The test coverage remains the same with this change, but the test
won't break due to internal refactoring.
This test was added in commit 793dc676e0 ("grep/icase: avoid kwsset
when -F is specified", 2016-06-25). It was asserting that the regex
must be compiled with compile_fixed_regexp(), instead test for the
expected results, allowing the underlying implementation to change.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a test for backreferences such as (.)\1 in PCRE patterns. This
test ensures that the PCRE_NO_AUTO_CAPTURE option isn't turned
on. Before this change turning it on would break these sort of
patterns, but wouldn't break any tests.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a test asserting that when --perl-regexp (and -P for grep) is
given to git-grep & git-log that we die with an error.
In developing the PCRE v2 series I introduced a regression where -P
would (through control-flow fall-through) become synonymous with basic
POSIX matching. I.e. 'git grep -P '[\d]' would match "d" instead of
digits.
The entire test suite would still pass with this serious regression,
since everything that tested for --perl-regexp would be guarded by the
PCRE prerequisite, fix that blind-spot by adding tests under !PCRE
asserting that git must die when given --perl-regexp or -P.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make the --regexp-ignore-case option work with --perl-regexp. This
never worked, and there was no test for this. Fix the bug and add a
test.
When PCRE support was added in commit 63e7e9d8b6 ("git-grep: Learn
PCRE", 2011-05-09) compile_pcre_regexp() would only check
opt->ignore_case, but when the --perl-regexp option was added in
commit 727b6fc3ed ("log --grep: accept --basic-regexp and
--perl-regexp", 2012-10-03) the code didn't set the opt->ignore_case.
Change the test suite to test for -i and --invert-regexp with
basic/extended/perl patterns in addition to fixed, which was the only
patternType that was tested for before in combination with those
options.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add exhaustive tests for how the different grep.patternType options &
the corresponding command-line options affect git-log.
Before this change it was possible to patch revision.c so that the
--basic-regexp option was synonymous with --extended-regexp, and
--perl-regexp wasn't recognized at all, and still have 100% of the
test suite pass.
This was because the first test being modified here, added in commit
34a4ae55b2 ("log --grep: use the same helper to set -E/-F options as
"git grep"", 2012-10-03), didn't actually check whether we'd enabled
extended regular expressions as distinct from re-toggling non-fixed
string support.
Fix that by changing the pattern to a pattern that'll only match if
--extended-regexp option is provided, but won't match under the
default --basic-regexp option.
Other potential regressions were possible since there were no tests
for the rest of the combinations of grep.patternType configuration
toggles & corresponding git-log command-line options. Add exhaustive
tests for those.
The patterns being passed to fixed/basic/extended/PCRE are carefully
crafted to return the wrong thing if the grep engine were to pick any
other matching method than the one it's told to use.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Rename the LIBPCRE prerequisite to PCRE. This is for preparation for
libpcre2 support, where having just "LIBPCRE" would be confusing as it
implies v1 of the library.
None of these tests are incompatible between versions 1 & 2 of
libpcre, it's less confusing to give them a more general name to make
it clear that they work on both library versions.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Stop promising in our grep & rev-list options documentation that we're
always going to be using libpcre when given the --perl-regexp option.
Instead talk about using "Perl-compatible regular expressions" and
using these types of patterns using "a compile-time dependency".
Saying "libpcre" means that we're talking about libpcre.so, which is
always going to be v1. This change is part of an ongoing saga to add
support for libpcre2, which comes with PCRE v2.
In the future we might use some completely unrelated library to
provide perl-compatible regular expression support. By wording the
documentation differently and not promising any specific version of
PCRE or even PCRE at all we have more wiggle room to change the
implementation.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reword an outdated & inaccurate comment which suggests that only
git-grep can use PCRE.
This comment was added back when PCRE support was initially added in
commit 63e7e9d8b6 ("git-grep: Learn PCRE", 2011-05-09), and was true
at the time.
It hasn't been telling the full truth since git-log learned to use
PCRE with --grep in commit 727b6fc3ed ("log --grep: accept
--basic-regexp and --perl-regexp", 2012-10-03), and more importantly
is likely to get more inaccurate over time as more use is made of PCRE
in other areas.
Reword it to be more future-proof, and to more clearly explain that
this enables user-initiated runtime behavior.
Copy/pasting this so much in configure.ac is lame, these Makefile-like
flags aren't even used by autoconf, just the corresponding
--with[out]-* options. But copy/pasting the comments that make sense
for the Makefile to configure.ac where they make less sense is the
pattern everything else follows in that file. I'm not going to war
against that as part of this change, just following the existing
pattern.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
