[PATCH] checkpatch: Validate Fixes: tag using 'commit' checks

[Sean Christopherson]

Rework checkpatch's commit checking to explicitly include the Fixes:
tag so that it catches errors like too short[1] or fat fingered[2] SHA1
references.

Add a new Fixes-only check to verify the fixed commit is a valid object
in the repository.

[1] https://lkml.kernel.org/r/20190830010615.GC27970@xxxxxxxxxxxxxxx
[2] https://lkml.kernel.org/r/20190825233120.18ac25e4@xxxxxxxxxxxxxxxx

Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 scripts/checkpatch.pl | 39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 93a7edfe0f05..dead0eb41007 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2756,10 +2756,10 @@ sub process {
 		    $line !~ /^\s*(?:Link|Patchwork|http|https|BugLink):/i &&
 		    $line !~ /^This reverts commit [0-9a-f]{7,40}/ &&
 		    ($line =~ /\bcommit\s+[0-9a-f]{5,}\b/i ||
+		     $line =~ /\bfixes:\s*[0-9a-f]{5,}\b/i ||
 		     ($line =~ /(?:\s|^)[0-9a-f]{12,40}(?:[\s"'\(\[]|$)/i &&
-		      $line !~ /[\<\[][0-9a-f]{12,40}[\>\]]/i &&
-		      $line !~ /\bfixes:\s*[0-9a-f]{12,40}/i))) {
-			my $init_char = "c";
+		      $line !~ /[\<\[][0-9a-f]{12,40}[\>\]]/i))) {
+			my $init_tag = "";
 			my $orig_commit = "";
 			my $short = 1;
 			my $long = 0;
@@ -2771,29 +2771,31 @@ sub process {
 			my $orig_desc = "commit description";
 			my $description = "";
 
-			if ($line =~ /\b(c)ommit\s+([0-9a-f]{5,})\b/i) {
-				$init_char = $1;
+			if ($line =~ /\b(commit)\s+([0-9a-f]{5,})\b/i ||
+			    $line =~ /\b(fixes:)\s*([0-9a-f]{5,})\b/i) {
+				$init_tag = $1;
 				$orig_commit = lc($2);
 			} elsif ($line =~ /\b([0-9a-f]{12,40})\b/i) {
+				$init_tag = "commit";
 				$orig_commit = lc($1);
 			}
 
-			$short = 0 if ($line =~ /\bcommit\s+[0-9a-f]{12,40}/i);
-			$long = 1 if ($line =~ /\bcommit\s+[0-9a-f]{41,}/i);
-			$space = 0 if ($line =~ /\bcommit [0-9a-f]/i);
-			$case = 0 if ($line =~ /\b[Cc]ommit\s+[0-9a-f]{5,40}[^A-F]/);
-			if ($line =~ /\bcommit\s+[0-9a-f]{5,}\s+\("([^"]+)"\)/i) {
+			$short = 0 if ($line =~ /\b$init_tag\s+[0-9a-f]{12,40}/i);
+			$long = 1 if ($line =~ /\b$init_tag\s+[0-9a-f]{41,}/i);
+			$space = 0 if ($line =~ /\b$init_tag [0-9a-f]/i);
+			$case = 0 if ($line =~ /\b$init_tag\s+[0-9a-f]{5,40}[^A-F]/);
+			if ($line =~ /\b$init_tag\s+[0-9a-f]{5,}\s+\("([^"]+)"\)/i) {
 				$orig_desc = $1;
 				$hasparens = 1;
-			} elsif ($line =~ /\bcommit\s+[0-9a-f]{5,}\s*$/i &&
+			} elsif ($line =~ /\b$init_tag\s+[0-9a-f]{5,}\s*$/i &&
 				 defined $rawlines[$linenr] &&
 				 $rawlines[$linenr] =~ /^\s*\("([^"]+)"\)/) {
 				$orig_desc = $1;
 				$hasparens = 1;
-			} elsif ($line =~ /\bcommit\s+[0-9a-f]{5,}\s+\("[^"]+$/i &&
+			} elsif ($line =~ /\b$init_tag\s+[0-9a-f]{5,}\s+\("[^"]+$/i &&
 				 defined $rawlines[$linenr] &&
 				 $rawlines[$linenr] =~ /^\s*[^"]+"\)/) {
-				$line =~ /\bcommit\s+[0-9a-f]{5,}\s+\("([^"]+)$/i;
+				$line =~ /\b$init_tag\s+[0-9a-f]{5,}\s+\("([^"]+)$/i;
 				$orig_desc = $1;
 				$rawlines[$linenr] =~ /^\s*([^"]+)"\)/;
 				$orig_desc .= " " . $1;
@@ -2803,10 +2805,15 @@ sub process {
 			($id, $description) = git_commit_info($orig_commit,
 							      $id, $orig_desc);
 
-			if (defined($id) &&
-			   ($short || $long || $space || $case || ($orig_desc ne $description) || !$hasparens)) {
+
+			if (!defined($id)) {
+				if ($init_tag =~ /fixes:/i) {
+					ERROR("GIT_COMMIT_ID",
+					      "Target SHA1 '$orig_commit' does not exist\n" . $herecurr);
+				}
+			} elsif ($short || $long || $space || $case || ($orig_desc ne $description) || !$hasparens) {
 				ERROR("GIT_COMMIT_ID",
-				      "Please use git commit description style 'commit <12+ chars of sha1> (\"<title line>\")' - ie: '${init_char}ommit $id (\"$description\")'\n" . $herecurr);
+				      "Please use git commit description style '$init_tag <12+ chars of sha1> (\"<title line>\")' - ie: '$init_tag $id (\"$description\")'\n" . $herecurr);
 			}
 		}
 
-- 
2.22.0