[PATCH v2 00/13] PCRE v1 improvements & PCRE v2 support

It's been a while since I sent v1 of this. I addressed most of the comments, except:

 * grep w/submodules doesn't properly pcre2 to submodule greps.

 * The critiqued adding runtime complexity by supporting both pcre1 &
   pcre2 via a switch is still there.

I wanted to get something out the door to review the other bits I've changed sooner than later, so I'm sending it in the state it's in. Depending on the consensus for those two issues, fixes for those can easily be addedd on top.

Comments on specific patches:

Ævar Arnfjörð Bjarmason (13):

Firstly, the "git grep --threads=N" patch is missing, that became the independent "[PATCH v2 0/8] grep threading cleanup & tests" series. See <20170416222102.2320-1-avarab@gmail.com>.

  grep: remove redundant regflags assignment under PCRE

No changes.

  Makefile & configure: reword outdated comment about PCRE

Fix comment copy as suggested by JK, and explained the confusing copy/pasting of Makefile comments to configure.ac in the commit message.

  grep: add a test for backreferences in PCRE patterns

No changes.

  log: add exhaustive tests for pattern style options & config

Now using [\d] instead of \((?=1) as a pattern to tell -E and -P patterns apart, as suggested by JK.

  log: add -P as a synonym for --perl-regexp

Uses the [\d] pattern now for a test, no other changes.

  grep & rev-list doc: stop promising libpcre for --perl-regexp

No changes.

  grep: make grep.patternType=[pcre|pcre1] a synonym for "perl"

Minor grammar fix in commit message.

  test-lib: rename the LIBPCRE prerequisite to PCRE

No changes.

  grep: change the internal PCRE macro names to be PCRE1

No changes.

  grep: change the internal PCRE code & header names to be PCRE1

No changes.

  perf: add a performance comparison test of grep -E and -P

NEW: Instead of my huge perl -MBenchmark one-liner I wrote a t/perf/
test for grep engine comparison which I'm citing for subsequent
changes.

  grep: add support for the PCRE v1 JIT API

NEW: Adds JIT support for PCRE v1.

  grep: add support for PCRE v2

Lots of changes:

 - Much smaller and hopefully less confusing commit message &
   discussion of performance differences.

 - Much improved PCRE v2 API use. The Zoltán Herczeg on the pcre-dev
   list helped a lot with that. Now less buggy & more performant.

 - Plugged a trivial memory leak I missed in v1.

Ævar Arnfjörð Bjarmason (13):
  grep: remove redundant regflags assignment under PCRE
  Makefile & configure: reword outdated comment about PCRE
  grep: add a test for backreferences in PCRE patterns
  log: add exhaustive tests for pattern style options & config
  log: add -P as a synonym for --perl-regexp
  grep & rev-list doc: stop promising libpcre for --perl-regexp
  grep: make grep.patternType=[pcre|pcre1] a synonym for "perl"
  test-lib: rename the LIBPCRE prerequisite to PCRE
  grep: change the internal PCRE macro names to be PCRE1
  grep: change the internal PCRE code & header names to be PCRE1
  perf: add a performance comparison test of grep -E and -P
  grep: add support for the PCRE v1 JIT API
  grep: add support for PCRE v2

 Documentation/config.txt           |   7 ++
 Documentation/git-grep.txt         |   4 +-
 Documentation/rev-list-options.txt |   6 +-
 Makefile                           |  28 ++++-
 configure.ac                       |  61 +++++++++-
 grep.c                             | 233 ++++++++++++++++++++++++++++++++-----
 grep.h                             |  36 +++++-
 revision.c                         |   2 +-
 t/README                           |  16 ++-
 t/perf/p7820-grep-engines.sh       |  25 ++++
 t/t4202-log.sh                     |  86 +++++++++++++-
 t/t7810-grep.sh                    |  69 ++++++++---
 t/t7812-grep-icase-non-ascii.sh    |   4 +-
 t/t7813-grep-icase-iso.sh          |  11 +-
 t/test-lib.sh                      |   4 +-
 15 files changed, 516 insertions(+), 76 deletions(-)
 create mode 100755 t/perf/p7820-grep-engines.sh