rerere.c: use symbolic constants to keep track of parsing states

These hardcoded integers make the code harder to follow than necessary;
replace them with enums to make it easier to read, before adding support
for optionally parsing "diff3 -m" style conflict markers.

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

rerere.c

@@ -75,7 +75,10 @@ static int handle_file(const char *path,
 {
 	SHA_CTX ctx;
 	char buf[1024];
-	int hunk = 0, hunk_no = 0;
+	int hunk_no = 0;
+	enum {
+		RR_CONTEXT = 0, RR_SIDE_1, RR_SIDE_2,
+	} hunk = RR_CONTEXT;
 	struct strbuf one, two;
 	FILE *f = fopen(path, "r");
 	FILE *out = NULL;
@@ -98,20 +101,20 @@ static int handle_file(const char *path,
 	strbuf_init(&two,  0);
 	while (fgets(buf, sizeof(buf), f)) {
 		if (!prefixcmp(buf, "<<<<<<< ")) {
-			if (hunk)
+			if (hunk != RR_CONTEXT)
 				goto bad;
-			hunk = 1;
+			hunk = RR_SIDE_1;
 		} else if (!prefixcmp(buf, "=======") && isspace(buf[7])) {
-			if (hunk != 1)
+			if (hunk != RR_SIDE_1)
 				goto bad;
-			hunk = 2;
+			hunk = RR_SIDE_2;
 		} else if (!prefixcmp(buf, ">>>>>>> ")) {
-			if (hunk != 2)
+			if (hunk != RR_SIDE_2)
 				goto bad;
 			if (strbuf_cmp(&one, &two) > 0)
 				strbuf_swap(&one, &two);
 			hunk_no++;
-			hunk = 0;
+			hunk = RR_CONTEXT;
 			if (out) {
 				fputs("<<<<<<<\n", out);
 				fwrite(one.buf, one.len, 1, out);
@@ -127,9 +130,9 @@ static int handle_file(const char *path,
 			}
 			strbuf_reset(&one);
 			strbuf_reset(&two);
-		} else if (hunk == 1)
+		} else if (hunk == RR_SIDE_1)
 			strbuf_addstr(&one, buf);
-		else if (hunk == 2)
+		else if (hunk == RR_SIDE_2)
 			strbuf_addstr(&two, buf);
 		else if (out)
 			fputs(buf, out);
@@ -146,7 +149,7 @@ static int handle_file(const char *path,
 		fclose(out);
 	if (sha1)
 		SHA1_Final(sha1, &ctx);
-	if (hunk) {
+	if (hunk != RR_CONTEXT) {
 		if (output)
 			unlink(output);
 		return error("Could not parse conflict hunks in %s", path);