[PATCH v2] chainlint: colorize problem annotations and test delimiters

From: Eric Sunshine <sunshine@sunshineco.com>

When `chainlint.pl` detects problems in a test definition, it emits the test definition with "?!FOO?!" annotations highlighting the problems it discovered. For instance, given this problematic test:

    test_expect_success 'discombobulate frobnitz' '
        git frob babble &&
        (echo balderdash; echo gnabgib) >expect &&
        for i in three two one
        do
            git nitfol $i
        done >actual
        test_cmp expect actual
    '

chainlint.pl will output:

    # chainlint: t1234-confusing.sh
    # chainlint: discombobulate frobnitz
    git frob babble &&
    (echo balderdash ; ?!AMP?! echo gnabgib) >expect &&
    for i in three two one
    do
    git nitfol $i ?!LOOP?!
    done >actual ?!AMP?!
    test_cmp expect actual

in which it may be difficult to spot the "?!FOO?!" annotations. The problem is compounded when multiple tests, possibly in multiple scripts, fail "linting", in which case it may be difficult to spot the "# chainlint:" lines which delimit one problematic test from another.

To ameliorate this potential problem, colorize the "?!FOO?!" annotations in order to quickly draw the test author's attention to the problem spots, and colorize the "# chainlint:" lines to help the author identify the name of each script and each problematic test.

Colorization is disabled automatically if output is not directed to a terminal or if NO_COLOR environment variable is set. The implementation is specific to Unix (it employs `tput` if available) but works equally well in the Git for Windows development environment which emulates Unix sufficiently.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
---
    chainlint: colorize problem annotations and test delimiters
    
    This is a re-roll of [1] which colorizes the output of "chainlint.pl"
    when it detects problems in Git test definitions. During discussion, it
    was noted that the eye could sometimes glide right over[2] the bold-red
    "?!FOO?!" annotations, so Junio suggested using reverse video, which is
    what v2 does.
    
    Reverse video certainly makes the "?!FOO?!" annotations pop out and draw
    the reader's attention. I find that I don't have a strong preference
    between this version and v1 which merely used bold-red, but I suspect
    that v2 with its reverse video is probably the better approach.
    
    [1]
    https://lore.kernel.org/git/pull.1324.git.git.1663023888412.gitgitgadget@gmail.com/
    [2]
    https://lore.kernel.org/git/CAPig+cTq3j5M7cz3T14h9U6e+H5PAu8JJ_Svq87W3WviwS6_qA@mail.gmail.com/
    [3] https://lore.kernel.org/git/xmqqo7vkazuh.fsf@gitster.g/

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1324%2Fsunshineco%2Fchainlintcolor-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1324/sunshineco/chainlintcolor-v2
Pull-Request: https://github.com/git/git/pull/1324

Range-diff vs v1:

 1:  d670570e81f ! 1:  acf9183ccc6 chainlint: colorize problem annotations and test delimiters
     @@ t/chainlint.pl: sub check_test {
       	$checked =~ s/^\n//;
       	$checked =~ s/^ //mg;
       	$checked =~ s/ $//mg;
     -+	$checked =~ s/(\?![^?]+\?!)/$c->{bold}$c->{red}$1$c->{reset}/mg;
     ++	$checked =~ s/(\?![^?]+\?!)/$c->{rev}$c->{red}$1$c->{reset}/mg;
       	$checked .= "\n" unless $checked =~ /\n$/;
      -	push(@{$self->{output}}, "# chainlint: $title\n$checked");
      +	push(@{$self->{output}}, "$c->{blue}# chainlint: $title$c->{reset}\n$checked");
     @@ t/chainlint.pl: if (eval {require Time::HiRes; Time::HiRes->import(); 1;}) {
      +# thread and ignore %ENV changes in subthreads.
      +$ENV{TERM} = $ENV{USER_TERM} if $ENV{USER_TERM};
      +
     -+my @NOCOLORS = (bold => '', reset => '', blue => '', green => '', red => '');
     ++my @NOCOLORS = (bold => '', rev => '', reset => '', blue => '', green => '', red => '');
      +my %COLORS = ();
      +sub get_colors {
      +	return \%COLORS if %COLORS;
      +	if (exists($ENV{NO_COLOR}) ||
      +	    system("tput sgr0 >/dev/null 2>&1") != 0 ||
      +	    system("tput bold >/dev/null 2>&1") != 0 ||
     ++	    system("tput rev  >/dev/null 2>&1") != 0 ||
      +	    system("tput setaf 1 >/dev/null 2>&1") != 0) {
      +		%COLORS = @NOCOLORS;
      +		return \%COLORS;
      +	}
      +	%COLORS = (bold  => `tput bold`,
     ++		   rev   => `tput rev`,
      +		   reset => `tput sgr0`,
      +		   blue  => `tput setaf 4`,
      +		   green => `tput setaf 2`,

 t/chainlint.pl | 46 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 43 insertions(+), 3 deletions(-)