merge-recursive: use subtraction to flip stage

gitster · gitster · commit 4c616c2ba1c1 · 2020-01-27T11:17:41.000-08:00
The flip_stage() helper uses a bit-flipping xor to switch between "2"
and "3". While clever, this relies on a property of those two numbers
that is mostly coincidence. Let's write it as a subtraction; that's more
clear and would extend to other numbers if somebody copies the logic.

Signed-off-by: Jeff King &lt;peff@peff.net&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/merge-recursive.c b/merge-recursive.c
@@ -1713,12 +1713,11 @@ static char *find_path_for_conflict(struct merge_options *opt,
 }
 
 /*
- * Toggle the stage number between "ours" and "theirs" (2 and 3) by flipping
- * the 1-bit.
+ * Toggle the stage number between "ours" and "theirs" (2 and 3).
  */
 static inline int flip_stage(int stage)
 {
-	return stage ^ 1;
+	return (2 + 3) - stage;
 }
 
 static int handle_rename_rename_1to2(struct merge_options *opt,

Original file line number	Diff line number	Diff line change
`@@ -1713,12 +1713,11 @@ static char find_path_for_conflict(struct merge_options opt,`
`1713`	`1713`	`}`
`1714`	`1714`
`1715`	`1715`	`/*`
`1716`		`- * Toggle the stage number between "ours" and "theirs" (2 and 3) by flipping`
`1717`		`- * the 1-bit.`
	`1716`	`+ * Toggle the stage number between "ours" and "theirs" (2 and 3).`
`1718`	`1717`	`*/`
`1719`	`1718`	`static inline int flip_stage(int stage)`
`1720`	`1719`	`{`
`1721`		`- return stage ^ 1;`
	`1720`	`+ return (2 + 3) - stage;`
`1722`	`1721`	`}`
`1723`	`1722`
`1724`	`1723`	`static int handle_rename_rename_1to2(struct merge_options *opt,`