[PATCH v7] checkpatch: warn for non-standard fixes tag style

[Niklas Söderlund]

Add a warning for fixes tags that does not follow community conventions.

Signed-off-by: Niklas Söderlund <niklas.soderlund@xxxxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Reviewed-by: Louis Peens <louis.peens@xxxxxxxxxxxx>
Reviewed-by: Philippe Schenker <philippe.schenker@xxxxxxxxxxx>
Acked-by: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx>
Reviewed-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Acked-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
---
* Changes since v6
- Update first check to make sure that there is a likely SHA1 of some
  minimum length after the fixes line.
- s/fall in line with community standard/follow community conventions/.
- Improve grammar, thanks Lukas.

* Changes since v5
- Add support for --fix option for checkpatch.pl.

* Changes since v4
- Extend test to cover lines with whitespace before the fixes: tag, e.g.
  match check on /^\s*fixes:?/i.

* Changes since v3
- Add test that title in tag match title of commit referenced by sha1.

* Changes since v2
- Change the pattern to match on 'fixes:?' to catch more malformed
  tags.

* Changes since v1
- Update the documentation wording and add mention one cause of the
  message can be that email program splits the tag over multiple lines.
---
 Documentation/dev-tools/checkpatch.rst |  7 ++++
 scripts/checkpatch.pl                  | 44 ++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
index b52452bc2963..c3389c6f3838 100644
--- a/Documentation/dev-tools/checkpatch.rst
+++ b/Documentation/dev-tools/checkpatch.rst
@@ -612,6 +612,13 @@ Commit message
 
     See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
 
+  **BAD_FIXES_TAG**
+    The Fixes: tag is malformed or does not follow the community conventions.
+    This can occur if the tag have been split into multiple lines (e.g., when
+    pasted in an email program with word wrapping enabled).
+
+    See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes
+
 
 Comparison style
 ----------------
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 79e759aac543..ddc5c9d730c3 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3140,6 +3140,50 @@ sub process {
 			}
 		}
 
+# Check Fixes: styles is correct
+		if (!$in_header_lines &&
+		    $line =~ /^\s*fixes:?\s*(?:commit\s*)?[0-9a-f]{5,}\b/i) {
+			my $orig_commit = "";
+			my $id = "0123456789ab";
+			my $title = "commit title";
+			my $tag_case = 1;
+			my $tag_space = 1;
+			my $id_length = 1;
+			my $id_case = 1;
+			my $title_has_quotes = 0;
+
+			if ($line =~ /(\s*fixes:?)\s+([0-9a-f]{5,})\s+($balanced_parens)/i) {
+				my $tag = $1;
+				$orig_commit = $2;
+				$title = $3;
+
+				$tag_case = 0 if $tag eq "Fixes:";
+				$tag_space = 0 if ($line =~ /^fixes:? [0-9a-f]{5,} ($balanced_parens)/i);
+
+				$id_length = 0 if ($orig_commit =~ /^[0-9a-f]{12}$/i);
+				$id_case = 0 if ($orig_commit !~ /[A-F]/);
+
+				# Always strip leading/trailing parens then double quotes if existing
+				$title = substr($title, 1, -1);
+				if ($title =~ /^".*"$/) {
+					$title = substr($title, 1, -1);
+					$title_has_quotes = 1;
+				}
+			}
+
+			my ($cid, $ctitle) = git_commit_info($orig_commit, $id,
+							     $title);
+
+			if ($ctitle ne $title || $tag_case || $tag_space ||
+			    $id_length || $id_case || !$title_has_quotes) {
+				if (WARN("BAD_FIXES_TAG",
+				     "Please use correct Fixes: style 'Fixes: <12 chars of sha1> (\"<title line>\")' - ie: 'Fixes: $cid (\"$ctitle\")'\n" . $herecurr) &&
+				    $fix) {
+					$fixed[$fixlinenr] = "Fixes: $cid (\"$ctitle\")";
+				}
+			}
+		}
+
 # Check email subject for common tools that don't need to be mentioned
 		if ($in_header_lines &&
 		    $line =~ /^Subject:.*\b(?:checkpatch|sparse|smatch)\b[^:]/i) {
-- 
2.37.3