Merge pull request #213 from jprotze/page-ranges

Merge page ranges for minimal diffs

latexdiff-vc

@@ -546,15 +546,15 @@ foreach $diff ( @difffiles ) {
       #print STDERR "Generated postscript file $ps\n";
     } elsif ( $run ) {
       if ( $onlychanges ) {
-	my @pages=findchangedpages("$diffbase.aux");
+	my @pages=compresspages(findchangedpages("$diffbase.aux"));
         my $gs = `which gs`;
         $gs =~ s/^\s+|\s+$//g;
         my $qpdf = `which qpdf`;
         $qpdf =~ s/^\s+|\s+$//g;
         my $pdftk = `which pdftk`;
         $pdftk =~ s/^\s+|\s+$//g;
         my $command;
-        if (-x $gs && `gs --version` >= 9.20) {
+        if (-x $gs && `$gs --version` >= 9.20) {
           $command="gs -sDEVICE=pdfwrite -dNOPAUSE -dBATCH -dSAFER -sPageList=" . join(",", @pages) . " -sOutputFile=\"$diffbase-changedpage.pdf\" \"$diffbase.pdf\"";
         } elsif (-x $pdftk) {
           $command="pdftk \"$diffbase.pdf\" cat " . join(" ",@pages) . " output \"$diffbase-changedpage.pdf\"";
@@ -602,13 +602,52 @@ sub findchangedpages {
   return(sort {$a <=> $b} keys(%pages));
 }
 
+# inspired by a python version posted at https://stackoverflow.com/a/54714846/8136338
+# compresspages(@pages)
+# @pages: sorted array of unique integers (pages)
+# return a list of pages and page ranges. 3 or more consecutive numbers are merged into a "begin-end" string
+#
+# example: join(",", compresspages([1,3,4,5,7,8])) -> join(",", [1,"3-5",7,8]) -> "1,3-5,7,8"
+sub compresspages {
+  my (@pages) = @_;
+  my @res;
+  my $begin=$pages[0];
+  my $end =$pages[0];
+  my $page;
+  foreach $page ( @pages ) {
+    next if ($page == $begin);
+    if ($page == $end+1) { # handle continuous pages
+      $end = $page;
+      next;
+    } elsif ($begin == $end) { # push single continuous page
+      push @res, $begin;
+      $begin = $end = $page;
+    } elsif ($begin + 1 == $end) { # push two continuous pages
+      push @res, $begin, $end;
+      $begin = $end = $page;
+    } else { # push multiple continuous pages
+      push @res, "$begin-$end";
+      $begin = $end = $page;
+    }
+  }
+  # Finally just check in the same manner for the end element
+  if ($begin == $end) {
+    push @res, $begin;
+  } elsif ($begin + 1 == $end) {
+    push @res, $begin, $end;
+  } else {
+    push @res, "$begin-$end";
+  }
+  return @res;
+}
+
 # checkout_dir(rev,dirname)
 # checks out revision rev and stores it in dirname
 # uses global variables: $vc, $rootdir
 sub checkout_dir {
   my ($rev,$dirname)=@_;
 
-  unless (-e $dirname) { mkdir $dirname or die "Cannot mkdir $dirname ." ;}
+  unless (-e $dirname) { mkpath([ $dirname ]) or die "Cannot mkdir $dirname ." ;}
   if ( $vc eq "SVN" ) {
     system("svn checkout -r $rev $rootdir $dirname")==0 or die "Something went wrong in executing:  svn checkout -r $rev $rootdir $dirname";
   } elsif ( $vc eq "GIT" ) {