Allow combined diff to ignore white-spaces

The combined diff --cc output does not honor options to ignore
whitespace changes (-b, -w, and --ignore-space-at-eol).

Correct this by passing diff flags to diff engine, so that combined
diff behaves as normal diff does with spaces, and by coalescing
lines that are removed from both (or more) parents, honoring the
same rule to ignore whitespace changes.

With this change, a conflict-less merge done using a ignore-*
strategy option will not show any conflict if shown in combined-diff
using the same option.

Signed-off-by: Antoine Pelisse <apelisse@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 50 insertions, 7 deletions

diff --git a/combine-diff.c b/combine-diff.c
index 35d41cd56d..6288485965 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -5,6 +5,7 @@
 #include "diffcore.h"
 #include "quote.h"
 #include "xdiff-interface.h"
+#include "xdiff/xmacros.h"
 #include "log-tree.h"
 #include "refs.h"
 #include "userdiff.h"
@@ -122,7 +123,47 @@ static char *grab_blob(const unsigned char *sha1, unsigned int mode,
 	return blob;
 }
 
-static void append_lost(struct sline *sline, int n, const char *line, int len)
+static int match_string_spaces(const char *line1, int len1,
+			       const char *line2, int len2,
+			       long flags)
+{
+	if (flags & XDF_WHITESPACE_FLAGS) {
+		for (; len1 > 0 && XDL_ISSPACE(line1[len1 - 1]); len1--);
+		for (; len2 > 0 && XDL_ISSPACE(line2[len2 - 1]); len2--);
+	}
+
+	if (!(flags & (XDF_IGNORE_WHITESPACE | XDF_IGNORE_WHITESPACE_CHANGE)))
+		return (len1 == len2 && !memcmp(line1, line2, len1));
+
+	while (len1 > 0 && len2 > 0) {
+		len1--;
+		len2--;
+		if (XDL_ISSPACE(line1[len1]) || XDL_ISSPACE(line2[len2])) {
+			if ((flags & XDF_IGNORE_WHITESPACE_CHANGE) &&
+			    (!XDL_ISSPACE(line1[len1]) || !XDL_ISSPACE(line2[len2])))
+				return 0;
+
+			for (; len1 > 0 && XDL_ISSPACE(line1[len1]); len1--);
+			for (; len2 > 0 && XDL_ISSPACE(line2[len2]); len2--);
+		}
+		if (line1[len1] != line2[len2])
+			return 0;
+	}
+
+	if (flags & XDF_IGNORE_WHITESPACE) {
+		/* Consume remaining spaces */
+		for (; len1 > 0 && XDL_ISSPACE(line1[len1 - 1]); len1--);
+		for (; len2 > 0 && XDL_ISSPACE(line2[len2 - 1]); len2--);
+	}
+
+	/* We matched full line1 and line2 */
+	if (!len1 && !len2)
+		return 1;
+
+	return 0;
+}
+
+static void append_lost(struct sline *sline, int n, const char *line, int len, long flags)
 {
 	struct lline *lline;
 	unsigned long this_mask = (1UL<<n);
@@ -133,8 +174,8 @@ static void append_lost(struct sline *sline, int n, const char *line, int len)
 	if (sline->lost_head) {
 		lline = sline->next_lost;
 		while (lline) {
-			if (lline->len == len &&
-			    !memcmp(lline->line, line, len)) {
+			if (match_string_spaces(lline->line, lline->len,
+						line, len, flags)) {
 				lline->parent_map |= this_mask;
 				sline->next_lost = lline->next;
 				return;
@@ -162,6 +203,7 @@ struct combine_diff_state {
 	int n;
 	struct sline *sline;
 	struct sline *lost_bucket;
+	long flags;
 };
 
 static void consume_line(void *state_, char *line, unsigned long len)
@@ -201,7 +243,7 @@ static void consume_line(void *state_, char *line, unsigned long len)
 		return; /* not in any hunk yet */
 	switch (line[0]) {
 	case '-':
-		append_lost(state->lost_bucket, state->n, line+1, len-1);
+		append_lost(state->lost_bucket, state->n, line+1, len-1, state->flags);
 		break;
 	case '+':
 		state->sline[state->lno-1].flag |= state->nmask;
@@ -215,7 +257,7 @@ static void combine_diff(const unsigned char *parent, unsigned int mode,
 			 struct sline *sline, unsigned int cnt, int n,
 			 int num_parent, int result_deleted,
 			 struct userdiff_driver *textconv,
-			 const char *path)
+			 const char *path, long flags)
 {
 	unsigned int p_lno, lno;
 	unsigned long nmask = (1UL << n);
@@ -231,9 +273,10 @@ static void combine_diff(const unsigned char *parent, unsigned int mode,
 	parent_file.ptr = grab_blob(parent, mode, &sz, textconv, path);
 	parent_file.size = sz;
 	memset(&xpp, 0, sizeof(xpp));
-	xpp.flags = 0;
+	xpp.flags = flags;
 	memset(&xecfg, 0, sizeof(xecfg));
 	memset(&state, 0, sizeof(state));
+	state.flags = flags;
 	state.nmask = nmask;
 	state.sline = sline;
 	state.lno = 1;
@@ -962,7 +1005,7 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
 				     elem->parent[i].mode,
 				     &result_file, sline,
 				     cnt, i, num_parent, result_deleted,
-				     textconv, elem->path);
+				     textconv, elem->path, opt->xdl_opts);
 	}
 
 	show_hunks = make_hunks(sline, cnt, num_parent, dense);