srtzip: Protect against accidentally overwriting an input file

srtzip.pike

@@ -12,6 +12,7 @@ int main(int argc,array(string) argv)
 
 	string outfn=files[-1]; files=files[..<1]-({outfn});
 	if (sizeof(files)<2) exit(0,"USAGE: pike %s input1.srt input2.srt [input3.srt...] output.srt\nAttempts to 'zip' the inputs into the output.\n");
+	if (!opt->clobber && file_stat(outfn)) exit(0,"Refusing to clobber %s\n",outfn);
 	write("Combining to %s:\n%{\t%s\n%}",outfn,files);
 	array(array(string)) inputs=String.trim_all_whites(utf8_to_string(Stdio.read_file(files[*])[*])[*])[*]/"\n\n";
 	//Trim off all index markers. We can re-add them later if they're wanted.