Merge branch 'ab/pickaxe-pcre2'

Rewrite the backend for "diff -G/-S" to use pcre2 engine when
available.

* ab/pickaxe-pcre2: (22 commits)
  xdiff-interface: replace discard_hunk_line() with a flag
  xdiff users: use designated initializers for out_line
  pickaxe -G: don't special-case create/delete
  pickaxe -G: terminate early on matching lines
  xdiff-interface: allow early return from xdiff_emit_line_fn
  xdiff-interface: prepare for allowing early return
  pickaxe -S: slightly optimize contains()
  pickaxe: rename variables in has_changes() for brevity
  pickaxe -S: support content with NULs under --pickaxe-regex
  pickaxe: assert that we must have a needle under -G or -S
  pickaxe: refactor function selection in diffcore-pickaxe()
  perf: add performance test for pickaxe
  pickaxe/style: consolidate declarations and assignments
  diff.h: move pickaxe fields together again
  pickaxe: die when --find-object and --pickaxe-all are combined
  pickaxe: die when -G and --pickaxe-regex are combined
  pickaxe tests: add missing test for --no-pickaxe-regex being an error
  pickaxe tests: test for -G, -S and --find-object incompatibility
  pickaxe tests: add test for "log -S" not being a regex
  pickaxe tests: add test for diffgrep_consume() internals
  ...

t/perf/p4209-pickaxe.sh

@@ -0,0 +1,70 @@
+#!/bin/sh
+
+test_description="Test pickaxe performance"
+
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+# Not --max-count, as that's the number of matching commit, so it's
+# unbounded. We want to limit our revision walk here.
+from_rev_desc=
+from_rev=
+max_count=1000
+if test_have_prereq EXPENSIVE
+then
+	max_count=10000
+fi
+from_rev=" $(git rev-list HEAD | head -n $max_count | tail -n 1).."
+from_rev_desc=" <limit-rev>.."
+
+for icase in \
+	'' \
+	'-i '
+do
+	# -S (no regex)
+	for pattern in \
+		'int main' \
+		'æ'
+	do
+		for opts in \
+			'-S'
+		do
+			test_perf "git log $icase$opts'$pattern'$from_rev_desc" "
+				git log --pretty=format:%H $icase$opts'$pattern'$from_rev
+			"
+		done
+	done
+
+	# -S (regex)
+	for pattern in  \
+		'(int|void|null)' \
+		'if *\([^ ]+ & ' \
+		'[àáâãäåæñøùúûüýþ]'
+	do
+		for opts in \
+			'--pickaxe-regex -S'
+		do
+			test_perf "git log $icase$opts'$pattern'$from_rev_desc" "
+				git log --pretty=format:%H $icase$opts'$pattern'$from_rev
+			"
+		done
+	done
+
+	# -G
+	for pattern in  \
+		'(int|void|null)' \
+		'if *\([^ ]+ & ' \
+		'[àáâãäåæñøùúûüýþ]'
+	do
+		for opts in \
+			'-G'
+		do
+			test_perf "git log $icase$opts'$pattern'$from_rev_desc" "
+				git log --pretty=format:%H $icase$opts'$pattern'$from_rev
+			"
+		done
+	done
+done
+
+test_done