checkpatch: emit an error when there's a diff in a changelog

People often put diff snippets in changelogs.  This causes problems
when one tries to apply a file containing both the changelog and the
diff because patch(1) tries to apply the diff which it found in the
changelog.

Warn once when what seems to be a diff snippet in the changelog exists.

Signed-off-by: Joe Perches <joe@perches.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
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 4cf4473..daf466d 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1954,6 +1954,7 @@ sub process {
        my $in_header_lines = $file ? 0 : 1;
        my $in_commit_log = 0;          #Scanning lines before patch
        my $commit_log_long_line = 0;
+       my $commit_log_has_diff = 0;
        my $reported_maintainer_file = 0;
        my $non_utf8_charset = 0;
 
@@ -2087,7 +2088,8 @@ sub process {
                my $rawline = $rawlines[$linenr - 1];
 
 #extract the line range in the file after the patch is applied
-               if ($line=~/^\@\@ -\d+(?:,\d+)? \+(\d+)(,(\d+))? \@\@/) {
+               if (!$in_commit_log &&
+                   $line =~ /^\@\@ -\d+(?:,\d+)? \+(\d+)(,(\d+))? \@\@/) {
                        $is_patch = 1;
                        $first_line = $linenr + 1;
                        $realline=$1-1;
@@ -2181,6 +2183,17 @@ sub process {
 
                $cnt_lines++ if ($realcnt != 0);
 
+# Check if the commit log has what seems like a diff which can confuse patch
+               if ($in_commit_log && !$commit_log_has_diff &&
+                   (($line =~ m@^\s+diff\b.*a/[\w/]+@ &&
+                     $line =~ m@^\s+diff\b.*a/([\w/]+)\s+b/$1\b@) ||
+                    $line =~ m@^\s*(?:\-\-\-\s+a/|\+\+\+\s+b/)@ ||
+                    $line =~ m/^\s*\@\@ \-\d+,\d+ \+\d+,\d+ \@\@/)) {
+                       ERROR("DIFF_IN_COMMIT_MSG",
+                             "Avoid using diff content in the commit message - patch(1) might not work\n" . $herecurr);
+                       $commit_log_has_diff = 1;
+               }
+
 # Check for incorrect file permissions
                if ($line =~ /^new (file )?mode.*[7531]\d{0,2}$/) {
                        my $permhere = $here . "FILE: $realfile\n";