Re: [PATCH v2 1/1] scripts: check commit message length to fit 75 characters

[Markus Armbruster]

"Denis V. Lunev" <den@openvz.org> writes:

> There are a lot of commits descriptions which are rendered in the
> 'git log' with line wrap. Apparently, this is looking awkward. Let us
> add check into checkpatch.pl for that.
>
> I am not very good Perl developer, but there is an implementation in
> Linux kernel's checkpatch.pl. Linux kernel people have faced a lot of
> obstacles here thus direct port from them looks beneficial.
>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Alexey Kardashevskiy <aik@ozlabs.ru>
> CC: "Philippe Mathieu-Daudé" <f4bug@amsat.org>
> CC: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> CC: Paolo Bonzini <pbonzini@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> CC: Markus Armbruster <armbru@redhat.com>
> ---
> Changes from v1:
> - fixed formatting to match one in the checkpatch.pl file. That was not
>   obvious :(
>
>  scripts/checkpatch.pl | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index d900d18048..fe1ff6c97d 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -36,6 +36,18 @@ my $root;
>  my %debug;
>  my $help = 0;
>  
> +our $signature_tags = qr{(?xi:
> +     Signed-off-by:|
> +     Co-developed-by:|
> +     Acked-by:|
> +     Tested-by:|
> +     Reviewed-by:|
> +     Reported-by:|
> +     Suggested-by:|
> +     To:|
> +     Cc:
> +)};
> +
>  sub help {
>       my ($exitcode) = @_;
>  
> @@ -1303,6 +1315,7 @@ 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 $reported_maintainer_file = 0;
>       my $non_utf8_charset = 0;
>  
> @@ -1585,6 +1598,19 @@ sub process {
>                       WARN("8-bit UTF-8 used in possible commit log\n" . 
> $herecurr);
>               }
>  
> +             if ($in_commit_log && !$commit_log_long_line && length($line) > 
> 75 &&
> +                 !($line =~ /^\s*[a-zA-Z0-9_\/\.]+\s+\|\s+\d+/ ||
> +                            # file delta changes
> +                   $line =~ /^\s*(?:[\w\.\-\+]*\/)++[\w\.\-\+]+:/ ||
> +                            # filename then :
> +                   $line =~ /^\s*(?:Fixes:|Link:|$signature_tags)/i
> +                            # A Fixes: or Link: line or signature tag line
> +                   )) {
> +                     WARN("Possible unwrapped commit description (prefer a 
> maximum " .
> +                          "75 chars per line)\n" . $herecurr);
> +                     $commit_log_long_line = 1;
> +             }
> +
>  # ignore non-hunk lines and lines being removed
>               next if (!$hunk_line || $line =~ /^-/);

For comparison, Linux's version:

   # Check for line lengths > 75 in commit log, warn once
                   if ($in_commit_log && !$commit_log_long_line &&
                       length($line) > 75 &&
                       !($line =~ /^\s*[a-zA-Z0-9_\/\.]+\s+\|\s+\d+/ ||
                                           # file delta changes
                         $line =~ /^\s*(?:[\w\.\-\+]*\/)++[\w\.\-\+]+:/ ||
                                           # filename then :
                         $line =~ /^\s*(?:Fixes:|Link:|$signature_tags)/i ||
                                           # A Fixes: or Link: line or 
signature tag line
                         $commit_log_possible_stack_dump)) {
                           WARN("COMMIT_LOG_LONG_LINE",
                                "Possible unwrapped commit description (prefer 
a maximum 75 chars per line)\n" . $herecurr);
                           $commit_log_long_line = 1;
                   }

Differences:

* Initial comment lost.  Let's add it back.

* One fewer line break, and spaces instead of tabs.  I think it's best
  to stick to the original there.

* We don't have $commit_log_possible_stack_dump.  Should we?

Initial Linux version was

    2a076f40d8c9 checkpatch, SubmittingPatches: suggest line wrapping
    commit messages at 75 columns

Updates since:

    369c8dd390ba checkpatch: improve tests for fixes:, long lines and
    stack dumps in commit log

    27b379af6102 checkpatch: avoid COMMIT_LOG_LONG_LINE warning for
    signature tags

    36f8b348a94c checkpatch: relax regexp for COMMIT_LOG_LONG_LINE

The first of these also messes with $commit_log_possible_stack_dump.
Added before in

    bf4daf12a9fb checkpatch: avoid some commit message long line warnings

and updated later in

    634cffcc9478 checkpatch: don't interpret stack dumps as commit IDs