be4311c07e14feb728abc6425ee606ffaa611a58
markd
  Fri Jan 22 06:46:58 2021 -0800
merge with master

diff --git src/lib/bwgCreate.c src/lib/bwgCreate.c
index 7f22244..d2eeadb 100644
--- src/lib/bwgCreate.c
+++ src/lib/bwgCreate.c
@@ -442,31 +442,31 @@
 if (chrom == NULL)
     errAbort("Missing chrom= setting line %d of %s\n", lf->lineIx, lf->fileName);
 
 bits32 chromSize = getChromSize(chromSizeHash, chrom, clipDontDie);
 
 if (start > chromSize)
     {
     warn("line %d of %s: chromosome %s has %u bases, but item starts at %u",
     	lf->lineIx, lf->fileName, chrom, chromSize, start);
     if (!clipDontDie)
         noWarnAbort();
     }
 if (type == bwgTypeFixedStep)
     {
     if (start == 0)
-	errAbort("Missing start= setting line %d of %s\n", lf->lineIx, lf->fileName);
+	errAbort("Missing start= setting line %d of %s. If start=0 was specified: wiggle is a 1-based format (sorry), so start has to be >= 1.\n", lf->lineIx, lf->fileName);
     if (step == 0)
 	errAbort("Missing step= setting line %d of %s\n", lf->lineIx, lf->fileName);
     if (span == 0)
 	span = step;
     parseFixedStepSection(lf, clipDontDie, lm, itemsPerSlot, 
     	chrom, chromSize, span, start-1, step, pSectionList);
     }
 else
     {
     if (start != 0)
 	errAbort("Extra start= setting line %d of %s\n", lf->lineIx, lf->fileName);
     if (step != 0)
 	errAbort("Extra step= setting line %d of %s\n", lf->lineIx, lf->fileName);
     if (span == 0)
 	span = 1;