[PATCH v2 1/2] xdiff: reassign xpparm_t.flags bits

[Junio C Hamano <gitster@pobox.com>]

We have packed the bits too tightly in such a way that it is not
easy to add a new type of whitespace ignoring option, a new type
of LCS algorithm, or a new type of post-cleanup heuristics.

Reorder bits a bit to give room for these three classes of options
to grow.  Also make use of XDF_WHITESPACE_FLAGS macro where we check
any of these bits are on, instead of using DIFF_XDL_TST() macro on
individual possibilities.  That way, the "is any of the bits on?"
code does not have to change when we add more ways to ignore
whitespaces.

While at it, add a comment in front of the bit definitions to
clarify in which structure these defined bits may appear.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 diff.c        |  4 +---
 xdiff/xdiff.h | 24 ++++++++++++++----------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/diff.c b/diff.c
index 74283d9001..790250fe86 100644
--- a/diff.c
+++ b/diff.c
@@ -3434,9 +3434,7 @@ void diff_setup_done(struct diff_options *options)
 	 * inside contents.
 	 */
 
-	if (DIFF_XDL_TST(options, IGNORE_WHITESPACE) ||
-	    DIFF_XDL_TST(options, IGNORE_WHITESPACE_CHANGE) ||
-	    DIFF_XDL_TST(options, IGNORE_WHITESPACE_AT_EOL))
+	if ((options->xdl_opts & XDF_WHITESPACE_FLAGS))
 		DIFF_OPT_SET(options, DIFF_FROM_CONTENTS);
 	else
 		DIFF_OPT_CLR(options, DIFF_FROM_CONTENTS);
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index b090ad8eac..cbf5d8e166 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -27,22 +27,26 @@
 extern "C" {
 #endif /* #ifdef __cplusplus */
 
+/* xpparm_t.flags */
+#define XDF_NEED_MINIMAL (1 << 0)
 
-#define XDF_NEED_MINIMAL (1 << 1)
-#define XDF_IGNORE_WHITESPACE (1 << 2)
-#define XDF_IGNORE_WHITESPACE_CHANGE (1 << 3)
-#define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 4)
-#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE | XDF_IGNORE_WHITESPACE_AT_EOL)
+#define XDF_IGNORE_WHITESPACE (1 << 1)
+#define XDF_IGNORE_WHITESPACE_CHANGE (1 << 2)
+#define XDF_IGNORE_WHITESPACE_AT_EOL (1 << 3)
+#define XDF_WHITESPACE_FLAGS (XDF_IGNORE_WHITESPACE | \
+			      XDF_IGNORE_WHITESPACE_CHANGE | \
+			      XDF_IGNORE_WHITESPACE_AT_EOL)
 
-#define XDF_PATIENCE_DIFF (1 << 5)
-#define XDF_HISTOGRAM_DIFF (1 << 6)
+#define XDF_IGNORE_BLANK_LINES (1 << 7)
+
+#define XDF_PATIENCE_DIFF (1 << 14)
+#define XDF_HISTOGRAM_DIFF (1 << 15)
 #define XDF_DIFF_ALGORITHM_MASK (XDF_PATIENCE_DIFF | XDF_HISTOGRAM_DIFF)
 #define XDF_DIFF_ALG(x) ((x) & XDF_DIFF_ALGORITHM_MASK)
 
-#define XDF_IGNORE_BLANK_LINES (1 << 7)
-
-#define XDF_INDENT_HEURISTIC (1 << 8)
+#define XDF_INDENT_HEURISTIC (1 << 23)
 
+/* xdemitconf_t.flags */
 #define XDL_EMIT_FUNCNAMES (1 << 0)
 #define XDL_EMIT_FUNCCONTEXT (1 << 2)
 
-- 
2.15.0-263-g47cc852023