perf: store subsection results in "test-results/$GIT_PERF_SUBSECTION/"

When tests are run for a subsection defined in a config file, it is
better if the results for the current subsection are not overwritting
the results of a previous subsection.

So let's store the results for a subsection in a subdirectory of
"test-results/" with the subsection name.

The aggregate.perl, when it is run for a subsection, should then
aggregate the results found in "test-results/$GIT_PERF_SUBSECTION/".

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/perf/aggregate.perl

@@ -69,12 +69,17 @@ if (not @tests) {
 	@tests = glob "p????-*.sh";
 }
 
+my $resultsdir = "test-results";
+if ($ENV{GIT_PERF_SUBSECTION} ne "") {
+	$resultsdir .= "/" . $ENV{GIT_PERF_SUBSECTION};
+}
+
 my @subtests;
 my %shorttests;
 for my $t (@tests) {
 	$t =~ s{(?:.*/)?(p(\d+)-[^/]+)\.sh$}{$1} or die "bad test name: $t";
 	my $n = $2;
-	my $fname = "test-results/$t.subtests";
+	my $fname = "$resultsdir/$t.subtests";
 	open my $fp, "<", $fname or die "cannot open $fname: $!";
 	for (<$fp>) {
 		chomp;
@@ -98,7 +103,7 @@ sub read_descr {
 my %descrs;
 my $descrlen = 4; # "Test"
 for my $t (@subtests) {
-	$descrs{$t} = $shorttests{$t}.": ".read_descr("test-results/$t.descr");
+	$descrs{$t} = $shorttests{$t}.": ".read_descr("$resultsdir/$t.descr");
 	$descrlen = length $descrs{$t} if length $descrs{$t}>$descrlen;
 }
 
@@ -138,7 +143,7 @@ for my $t (@subtests) {
 	my $firstr;
 	for my $i (0..$#dirs) {
 		my $d = $dirs[$i];
-		$times{$prefixes{$d}.$t} = [get_times("test-results/$prefixes{$d}$t.times")];
+		$times{$prefixes{$d}.$t} = [get_times("$resultsdir/$prefixes{$d}$t.times")];
 		my ($r,$u,$s) = @{$times{$prefixes{$d}.$t}};
 		my $w = length format_times($r,$u,$s,$firstr);
 		$colwidth[$i] = $w if $w > $colwidth[$i];

t/perf/perf-lib.sh

@@ -56,6 +56,7 @@ MODERN_GIT=$GIT_BUILD_DIR/bin-wrappers/git
 export MODERN_GIT
 
 perf_results_dir=$TEST_OUTPUT_DIRECTORY/test-results
+test -n "$GIT_PERF_SUBSECTION" && perf_results_dir="$perf_results_dir/$GIT_PERF_SUBSECTION"
 mkdir -p "$perf_results_dir"
 rm -f "$perf_results_dir"/$(basename "$0" .sh).subtests