perf: add performance test for pickaxe

Add a test for the -G and -S pickaxe options and related options.

This test supports being run with GIT_TEST_LONG=1 to adjust the limit
on the number of commits from 1k to 10k. The 1k limit seems to hit a
good spot on git.git

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

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