checkpatch: reduce number of `git log` calls with --git

checkpatch currently calls git log multiple times to first get the
<revision range> sha1 values and again to get the subject for each
individual sha1 commit.

Always get the sha1 and subject at the same time instead.  Store the
subject in a sha1 hash to avoid the second git log exec.

Link: http://lkml.kernel.org/r/274efab2332ad2308ab5de85a95d255f6e2de5f3.1462711962.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 8fc9edd..9283662 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -28,6 +28,7 @@ my $terse = 0;
 my $showfile = 0;
 my $file = 0;
 my $git = 0;
+my %git_commits = ();
 my $check = 0;
 my $check_orig = 0;
 my $summary = 1;
@@ -806,23 +807,25 @@ die "$P: No git repository found\n" if ($git && !-e ".git");
 
 if ($git) {
        my @commits = ();
-       for my $commit_expr (@ARGV) {
+       foreach my $commit_expr (@ARGV) {
                my $git_range;
                if ($commit_expr =~ m/-/) {
                        my @tmp = split(/-/, $commit_expr);
-                       die "$P: incorrect git commits expression $commit_expr$!\n"
+                       die "$P: incorrect git commit expression '$commit_expr' $!\n"
                            if (@tmp != 2);
                        $git_range = "-$tmp[1] $tmp[0]";
                } elsif ($commit_expr =~ m/\.\./) {
                        $git_range = "$commit_expr";
-               }
-               if (defined $git_range) {
-                       my $lines = `git log --no-merges --pretty=format:'%H' $git_range`;
-                       foreach my $line (split(/\n/, $lines)) {
-                               unshift(@commits, $line);
-                       }
                } else {
-                       unshift(@commits, $commit_expr);
+                       $git_range = "-1 $commit_expr";
+               }
+               my $lines = `git log --no-color --no-merges --pretty=format:'%H %s' $git_range`;
+               foreach my $line (split(/\n/, $lines)) {
+                       $line =~ /(^\w+) (.*)/;
+                       my $sha1 = $1;
+                       my $subject = $2;
+                       unshift(@commits, $sha1);
+                       $git_commits{$sha1} = $subject;
                }
        }
        die "$P: no git commits after extraction!\n" if (@commits == 0);
@@ -847,7 +850,7 @@ for my $filename (@ARGV) {
        if ($filename eq '-') {
                $vname = 'Your patch';
        } elsif ($git) {
-               $vname = "Commit " . substr($filename, 0, 12) . `git log -1 --pretty=format:' ("%s")' $filename`;
+               $vname = "Commit " . substr($filename, 0, 12) . ' ("' . $git_commits{$filename} . '")';
        } else {
                $vname = $filename;
        }