[PATCH] checkpatch: warn if changed lines exceeds a maximum size

[Brown, Nicholas]

Changed lines is the total of inserted and deleted lines.
By default there is no limit, --max-changed-lines may be used to set a
value. Some users may wish to encourage that patches are split into
smaller parts using this.
See Documentation/process/submitting-patches.rst#split-changes

Signed-off-by: Nicholas Brown <nick.brown@xxxxxxx>
---
 scripts/checkpatch.pl | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 31031f10fe56..1217d782b6bb 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -49,6 +49,7 @@ my @ignore = ();
 my $help = 0;
 my $configuration_file = ".checkpatch.conf";
 my $max_line_length = 80;
+my $max_changed_lines; # undef = no max
 my $ignore_perl_version = 0;
 my $minimum_perl_version = 5.10.0;
 my $min_conf_desc_length = 4;
@@ -209,6 +210,7 @@ GetOptions(
        'show-types!'   => \$show_types,
        'list-types!'   => \$list_types,
        'max-line-length=i' => \$max_line_length,
+       'max-changed-lines=i' => \$max_changed_lines,
        'min-conf-desc-length=i' => \$min_conf_desc_length,
        'root=s'        => \$root,
        'summary!'      => \$summary,
@@ -2165,6 +2167,8 @@ sub process {
        my $filename = shift;
 
        my $linenr=0;
+       my $inserted_lines_total=0;
+       my $deleted_lines_total=0;
        my $prevline="";
        my $prevrawline="";
        my $stashline="";
@@ -2233,6 +2237,14 @@ sub process {
 
                push(@fixed, $rawline) if ($fix);
 
+               if ($rawline=~/^\+/) {
+                 $inserted_lines_total++
+               }
+
+               if ($rawline=~/^-/) {
+                 $deleted_lines_total++
+               }
+
                if ($rawline=~/^\+\+\+\s+(\S+)/) {
                        $setup_docs = 0;
                        if ($1 =~ m@Documentation/admin-guide/kernel-parameters.rst$@) {
@@ -2306,6 +2318,11 @@ sub process {
 
        $prefix = '';
 
+       if (defined $max_changed_lines &&
+           ($inserted_lines_total+$deleted_lines_total > $max_changed_lines)) {
+         WARN("MAX_CHANGED_LINES", "please split the change into smaller parts\n");
+       }
+
        $realcnt = 0;
        $linenr = 0;
        $fixlinenr = -1;
-- 
2.14.1