FIX: ENTAB strips first character from line

fixes: Oldes/Rebol-issues#2216

Author: Oldes

src/core/s-ops.c

@@ -541,7 +541,10 @@ static REBYTE seed_str[SEED_LEN] = {
 
 			// Copy chars thru end-of-line (or end of buffer):
 			while (index < len) {
-				if ((*dp++ = bp[index++]) == '\n') break;
+				if ((*dp++ = bp[index++]) == '\n') {
+					index--;
+					break;
+				}
 			}
 		}
 	}
@@ -588,7 +591,10 @@ static REBYTE seed_str[SEED_LEN] = {
 
 			// Copy chars thru end-of-line (or end of buffer):
 			while (index < len) {
-				if ((*dp++ = bp[index++]) == '\n') break;
+				if ((*dp++ = bp[index++]) == '\n') {
+					index--;
+					break;
+				}
 			}
 		}
 	}

src/tests/units/series-test.r3

@@ -466,6 +466,23 @@ Rebol [
 
 ===end-group===
 
+===start-group=== "DETAB / ENTAB"
+
+--test-- "DETAB"
+	--assert "    A^/    B" = detab      "^-A^/^-B"
+	--assert "    A^/    Š" = detab      "^-A^/^-Š"
+	--assert "  A^/  B"     = detab/size "^-A^/^-B" 2
+	--assert "  A^/  Š"     = detab/size "^-A^/^-Š" 2
+--test-- "ENTAB"
+	;@@ https://github.com/Oldes/Rebol-issues/issues/2216
+	--assert "^-A^/^-B"     = entab      {    A^/    B}
+	--assert "^-A^/^-Š"     = entab      {    A^/    Š}
+	--assert "^-^-A^/^-^-B" = entab/size {    A^/    B} 2
+	--assert "^-^-A^/^-^-Š" = entab/size {    A^/    Š} 2
+	--assert "^-^-^- A"     = entab      {    ^-     A}
+
+===end-group===
+
 ===start-group=== "AS coercion"
 
 --test-- "AS datatype! any-string!"