merge-recursive: clarify code in was_tracked()

It can be puzzling to see that was_tracked() asks to get an index entry
by name, but does not take a negative return value for an answer.

The reason we have to do this is that cache_name_pos() only looks for
entries in stage 0, even if nobody asked for any stage in particular.

Let's rewrite the logic a little bit, to handle the easy case early: if
cache_name_pos() returned a non-negative position, we know it is a match,
and we do not even have to compare the name again (cache_name_pos() did
that for us already). We can say right away: yes, this file was tracked.

Only if there was no exact match do we need to look harder for any
matching entry in stage 2.
Signed-off-by: NJohannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -667,23 +667,21 @@ static int was_tracked(const char *path)
 {
 	int pos = cache_name_pos(path, strlen(path));
 
-	if (pos < 0)
-		pos = -1 - pos;
-	while (pos < active_nr &&
-	       !strcmp(path, active_cache[pos]->name)) {
-		/*
-		 * If stage #0, it is definitely tracked.
-		 * If it has stage #2 then it was tracked
-		 * before this merge started.  All other
-		 * cases the path was not tracked.
-		 */
-		switch (ce_stage(active_cache[pos])) {
-		case 0:
-		case 2:
+	if (0 <= pos)
+		/* we have been tracking this path */
+		return 1;
+
+	/*
+	 * Look for an unmerged entry for the path,
+	 * specifically stage #2, which would indicate
+	 * that "our" side before the merge started
+	 * had the path tracked (and resulted in a conflict).
+	 */
+	for (pos = -1 - pos;
+	     pos < active_nr && !strcmp(path, active_cache[pos]->name);
+	     pos++)
+		if (ce_stage(active_cache[pos]) == 2)
 			return 1;
-		}
-		pos++;
-	}
 	return 0;
 }