checkpatch: Print file line numbers

The line numbers being printed were the line numbers for the patchfile.
This is sometimes okay to fix simple things (trailing or leading
whitespace, missing signoffs, etc).  But more complicated fixes, or
those fixes which require a bit more care, aren't helped by this.  So,
we use the implied file line number.

This can be useful with future work to 'mock' apply and build a real
contextual scanner for checking multi-line changes.

Signed-off-by: Aaron Conole <[email protected]>
Signed-off-by: Ben Pfaff <[email protected]>

utilities/checkpatch.py

@@ -54,6 +54,7 @@ def print_warning(message, lineno=None):
 
 
 __regex_added_line = re.compile(r'^\+{1,2}[^\+][\w\W]*')
+__regex_subtracted_line = re.compile(r'^\-{1,2}[^\-][\w\W]*')
 __regex_leading_with_whitespace_at_all = re.compile(r'^\s+')
 __regex_leading_with_spaces = re.compile(r'^ +[\S]+')
 __regex_trailing_whitespace = re.compile(r'[^\S]+$')
@@ -79,6 +80,10 @@ def print_warning(message, lineno=None):
                          '.py']
 
 
+def is_subtracted_line(line):
+    """Returns TRUE if the line in question has been removed."""
+    return __regex_subtracted_line.search(line) is not None
+
 def is_added_line(line):
     """Returns TRUE if the line in question is an added line.
     """
@@ -150,6 +155,8 @@ def ovs_checkpatch_parse(text):
     previous_file = ''
     scissors = re.compile(r'^[\w]*---[\w]*')
     hunks = re.compile('^(---|\+\+\+) (\S+)')
+    hunk_differences = re.compile(
+        r'^@@ ([0-9-+]+),([0-9-+]+) ([0-9-+]+),([0-9-+]+) @@')
     is_signature = re.compile(r'((\s*Signed-off-by: )(.*))$',
                               re.I | re.M | re.S)
     is_co_author = re.compile(r'(\s*(Co-authored-by: )(.*))$',
@@ -199,6 +206,14 @@ def ovs_checkpatch_parse(text):
                 current_file = newfile.group(2)
                 print_file_name = current_file
                 continue
+            reset_line_number = hunk_differences.match(line)
+            if reset_line_number:
+                lineno = int(reset_line_number.group(3))
+                if lineno < 0:
+                    lineno = -1 * lineno
+                lineno -= 1
+            if is_subtracted_line(line):
+                lineno -= 1
             if not is_added_line(line):
                 continue
             # Skip files which have /datapath in them, since they are