[PATCH v2] Rewrite fsck.c:fsck_commit() replace memcmp() with starts_with()

[blacksimit <cengoguzhanunlu@gmail.com>]

From: Oguzhan Unlu <cengoguzhanunlu@gmail.com>

My solution to make lines containing buffer += a_number; clearer to anyone is following; I defined a new int, magic_num, then assigned lengths of used strings to magic_num and then changed assignment lines through using magic_num so that where the number which is added to buffer is known although I eliminated 3rd parameter of memcmp() when using starts_with().   

Signed-off-by: Oguzhan Unlu <cengoguzhanunlu@gmail.com>
---
 I didn't use skip_prefix() in this microproject and I plan to apply for GSOC 2014. I expect your feedbacks!
 fsck.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fsck.c b/fsck.c
index d43be98..4e5ca30 100644
--- a/fsck.c
+++ b/fsck.c
@@ -289,14 +289,17 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 	struct commit_graft *graft;
 	int parents = 0;
 	int err;
-
+    int magic_num;
+    
+    magic_num = strlen("tree "); /* magic_num is 5 */
 	if (!starts_with(buffer, "tree "))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'tree' line");
-	if (get_sha1_hex(buffer+5, tree_sha1) || buffer[45] != '\n')
+	if (get_sha1_hex(buffer+magic_num, tree_sha1) || buffer[45] != '\n')
 		return error_func(&commit->object, FSCK_ERROR, "invalid 'tree' line format - bad sha1");
 	buffer += 46;
+    magic_num = strlen("parent "); /* magic_num is 7 */
 	while (starts_with(buffer, "parent ")) {
-		if (get_sha1_hex(buffer+7, sha1) || buffer[47] != '\n')
+		if (get_sha1_hex(buffer+magic_num, sha1) || buffer[47] != '\n')
 			return error_func(&commit->object, FSCK_ERROR, "invalid 'parent' line format - bad sha1");
 		buffer += 48;
 		parents++;
@@ -322,15 +325,17 @@ static int fsck_commit(struct commit *commit, fsck_error error_func)
 		if (p || parents)
 			return error_func(&commit->object, FSCK_ERROR, "parent objects missing");
 	}
+    magic_num = strlen("author "); /* magic_num is 7 */
 	if (!starts_with(buffer, "author "))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'author' line");
-	buffer += 7;
+	buffer += magic_num;
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
+    magic_num = strlen("committer"); /* magic_num is 7 */
 	if (!starts_with(buffer, "committer "))
 		return error_func(&commit->object, FSCK_ERROR, "invalid format - expected 'committer' line");
-	buffer += strlen("committer ");
+	buffer += magic_num;
 	err = fsck_ident(&buffer, &commit->object, error_func);
 	if (err)
 		return err;
-- 
1.9.1.286.g5172cb3