whitespace: correct bit assignment comments

A comment in diff.c claimed that bits up to 12th (counting from 0th)
are whitespace rules, and 13th thru 15th are for new/old/context,
but it turns out it was miscounting.  Correct them, and clarify
where the whitespace rule bits come from in the comment.  Extend bit
assignment comments to cover bits used for color-moved, which
weren't described.

Also update the way these bit constants are defined to use (1 << N)
notation, instead of octal constants, as it tends to make it easier
to notice a breakage like this.

Sprinkle a few blank lines between logically distinct groups of CPP
macro definitions to make them easier to read.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/diff.c b/diff.c
index a74e701806..74261b332a 100644
--- a/diff.c
+++ b/diff.c
@@ -801,16 +801,19 @@ enum diff_symbol {
 	DIFF_SYMBOL_CONTEXT_MARKER,
 	DIFF_SYMBOL_SEPARATOR
 };
+
 /*
  * Flags for content lines:
- * 0..12 are whitespace rules
- * 13-15 are WSEH_NEW | WSEH_OLD | WSEH_CONTEXT
+ * 0..11 are whitespace rules (see ws.h)
+ * 12..14 are WSEH_NEW | WSEH_CONTEXT | WSEH_OLD
  * 16 is marking if the line is blank at EOF
+ * 17..19 are used for color-moved.
  */
 #define DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF	(1<<16)
 #define DIFF_SYMBOL_MOVED_LINE			(1<<17)
 #define DIFF_SYMBOL_MOVED_LINE_ALT		(1<<18)
 #define DIFF_SYMBOL_MOVED_LINE_UNINTERESTING	(1<<19)
+
 #define DIFF_SYMBOL_CONTENT_WS_MASK (WSEH_NEW | WSEH_OLD | WSEH_CONTEXT | WS_RULE_MASK)
 
 /*