xdiff: PATIENCE/HISTOGRAM are not independent option bitsjc/diff-algo-cleanup

Because the default Myers, patience and histogram algorithms cannot be in
effect at the same time, XDL_PATIENCE_DIFF and XDL_HISTOGRAM_DIFF are not
independent bits.  Instead of wasting one bit per algorithm, define a few
macros to access the few bits they occupy and update the code that access
them.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index 0c51724493..e688a48d10 100644
--- a/diff.h
+++ b/diff.h
@@ -88,6 +88,8 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_XDL_SET(opts, flag)    ((opts)->xdl_opts |= XDF_##flag)
 #define DIFF_XDL_CLR(opts, flag)    ((opts)->xdl_opts &= ~XDF_##flag)
 
+#define DIFF_WITH_ALG(opts, flag)   (((opts)->xdl_opts & ~XDF_DIFF_ALGORITHM_MASK) | XDF_##flag)
+
 enum diff_words_type {
 	DIFF_WORDS_NONE = 0,
 	DIFF_WORDS_PORCELAIN,