build: Add a script to format gcov report lines

Instead of using echo let's try Perl and the format() built-in.

build/Makefile.am

@@ -1 +1,3 @@
 SUBDIRS = autotools
+
+EXTRA_DIST = gen-gcov.pl

build/autotools/Makefile.am.gcov

@@ -11,7 +11,7 @@ gcov-report.txt: gcov-clean
 			covered=$$((actual - uncovered)); \
 			total_covered=$$((total_covered + covered)); \
 			total_actual=$$((total_actual + actual)); \
-			echo -e "$$file:    \t$$covered / $$actual\t($$((($$covered * 100) / $$actual))%)"; \
+			perl $(top_builddir)/build/gen-gcov.pl $$file.gcov; \
 		fi \
 	done >> $@; \
 	cd $(abs_srcdir); \

build/gen-gcov.pl

@@ -0,0 +1,44 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+our $gcov_file = $ARGV[0] or undef;
+
+open my $g, '<', $gcov_file
+    or die("Unable to open '$gcov_file': $!");
+
+my ($actual, $covered, $uncovered, $percent) = (0, 0, 0, 0);
+
+while (<$g>) {
+    my $report_line = $_;
+
+    chomp($report_line);
+
+    $actual += 1;
+    $actual -= 1 if $report_line =~ / -:/;
+
+    $uncovered += 1 if $report_line =~ /#####:/;
+}
+
+close($g);
+
+$covered = $actual - $uncovered;
+$percent = int(($covered * 100) / $actual);
+
+$gcov_file =~ s/^\.\///g;
+$gcov_file =~ s/\.gcov$//g;
+
+my $cover_file    = "$gcov_file:";
+my $cover_literal = "$covered / $actual";
+my $cover_percent = "$percent%";
+
+format ReportLine =
+@<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< @>>>>>>>>>>>>>  @>>>>>
+$cover_file,                                $cover_literal, $cover_percent
+.
+
+$~ = 'ReportLine';
+write;
+
+0;