builtin/apply: extract line_by_line_fuzzy_match() from match_fragment()

The match_fragment() function is very big and contains a big special case
algorithm that does line by line fuzzy matching. So let's extract this
algorithm in a separate line_by_line_fuzzy_match() function.

Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/apply.c

@@ -2242,6 +2242,74 @@ static void update_pre_post_images(struct image *preimage,
 	postimage->nr -= reduced;
 }
 
+static int line_by_line_fuzzy_match(struct image *img,
+				    struct image *preimage,
+				    struct image *postimage,
+				    unsigned long try,
+				    int try_lno,
+				    int preimage_limit)
+{
+	int i;
+	size_t imgoff = 0;
+	size_t preoff = 0;
+	size_t postlen = postimage->len;
+	size_t extra_chars;
+	char *buf;
+	char *preimage_eof;
+	char *preimage_end;
+	struct strbuf fixed;
+	char *fixed_buf;
+	size_t fixed_len;
+
+	for (i = 0; i < preimage_limit; i++) {
+		size_t prelen = preimage->line[i].len;
+		size_t imglen = img->line[try_lno+i].len;
+
+		if (!fuzzy_matchlines(img->buf + try + imgoff, imglen,
+				      preimage->buf + preoff, prelen))
+			return 0;
+		if (preimage->line[i].flag & LINE_COMMON)
+			postlen += imglen - prelen;
+		imgoff += imglen;
+		preoff += prelen;
+	}
+
+	/*
+	 * Ok, the preimage matches with whitespace fuzz.
+	 *
+	 * imgoff now holds the true length of the target that
+	 * matches the preimage before the end of the file.
+	 *
+	 * Count the number of characters in the preimage that fall
+	 * beyond the end of the file and make sure that all of them
+	 * are whitespace characters. (This can only happen if
+	 * we are removing blank lines at the end of the file.)
+	 */
+	buf = preimage_eof = preimage->buf + preoff;
+	for ( ; i < preimage->nr; i++)
+		preoff += preimage->line[i].len;
+	preimage_end = preimage->buf + preoff;
+	for ( ; buf < preimage_end; buf++)
+		if (!isspace(*buf))
+			return 0;
+
+	/*
+	 * Update the preimage and the common postimage context
+	 * lines to use the same whitespace as the target.
+	 * If whitespace is missing in the target (i.e.
+	 * if the preimage extends beyond the end of the file),
+	 * use the whitespace from the preimage.
+	 */
+	extra_chars = preimage_end - preimage_eof;
+	strbuf_init(&fixed, imgoff + extra_chars);
+	strbuf_add(&fixed, img->buf + try, imgoff);
+	strbuf_add(&fixed, preimage_eof, extra_chars);
+	fixed_buf = strbuf_detach(&fixed, &fixed_len);
+	update_pre_post_images(preimage, postimage,
+			       fixed_buf, fixed_len, postlen);
+	return 1;
+}
+
 static int match_fragment(struct image *img,
 			  struct image *preimage,
 			  struct image *postimage,
@@ -2331,61 +2399,9 @@ static int match_fragment(struct image *img,
 	 * fuzzy matching. We collect all the line length information because
 	 * we need it to adjust whitespace if we match.
 	 */
-	if (ws_ignore_action == ignore_ws_change) {
+	if (ws_ignore_action == ignore_ws_change)
-		size_t imgoff = 0;
+		return line_by_line_fuzzy_match(img, preimage, postimage,
-		size_t preoff = 0;
+						try, try_lno, preimage_limit);
-		size_t postlen = postimage->len;
-		size_t extra_chars;
-		char *preimage_eof;
-		char *preimage_end;
-		for (i = 0; i < preimage_limit; i++) {
-			size_t prelen = preimage->line[i].len;
-			size_t imglen = img->line[try_lno+i].len;
-
-			if (!fuzzy_matchlines(img->buf + try + imgoff, imglen,
-					      preimage->buf + preoff, prelen))
-				return 0;
-			if (preimage->line[i].flag & LINE_COMMON)
-				postlen += imglen - prelen;
-			imgoff += imglen;
-			preoff += prelen;
-		}
-
-		/*
-		 * Ok, the preimage matches with whitespace fuzz.
-		 *
-		 * imgoff now holds the true length of the target that
-		 * matches the preimage before the end of the file.
-		 *
-		 * Count the number of characters in the preimage that fall
-		 * beyond the end of the file and make sure that all of them
-		 * are whitespace characters. (This can only happen if
-		 * we are removing blank lines at the end of the file.)
-		 */
-		buf = preimage_eof = preimage->buf + preoff;
-		for ( ; i < preimage->nr; i++)
-			preoff += preimage->line[i].len;
-		preimage_end = preimage->buf + preoff;
-		for ( ; buf < preimage_end; buf++)
-			if (!isspace(*buf))
-				return 0;
-
-		/*
-		 * Update the preimage and the common postimage context
-		 * lines to use the same whitespace as the target.
-		 * If whitespace is missing in the target (i.e.
-		 * if the preimage extends beyond the end of the file),
-		 * use the whitespace from the preimage.
-		 */
-		extra_chars = preimage_end - preimage_eof;
-		strbuf_init(&fixed, imgoff + extra_chars);
-		strbuf_add(&fixed, img->buf + try, imgoff);
-		strbuf_add(&fixed, preimage_eof, extra_chars);
-		fixed_buf = strbuf_detach(&fixed, &fixed_len);
-		update_pre_post_images(preimage, postimage,
-				fixed_buf, fixed_len, postlen);
-		return 1;
-	}
 
 	if (ws_error_action != correct_ws_error)
 		return 0;