pass struct commit to diff_tree_combined_merge()

Instead of passing the hash of a commit and then searching that
same commit in the single caller, simply pass the commit directly.

Signed-off-by: René Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

combine-diff.c

@@ -1196,10 +1196,9 @@ void diff_tree_combined(const unsigned char *sha1,
 	}
 }
 
-void diff_tree_combined_merge(const unsigned char *sha1,
-			     int dense, struct rev_info *rev)
+void diff_tree_combined_merge(const struct commit *commit, int dense,
+			      struct rev_info *rev)
 {
-	struct commit *commit = lookup_commit(sha1);
 	struct commit_list *parent = commit->parents;
 	struct sha1_array parents = SHA1_ARRAY_INIT;
 
@@ -1207,6 +1206,6 @@ void diff_tree_combined_merge(const unsigned char *sha1,
 		sha1_array_append(&parents, parent->item->object.sha1);
 		parent = parent->next;
 	}
-	diff_tree_combined(sha1, &parents, dense, rev);
+	diff_tree_combined(commit->object.sha1, &parents, dense, rev);
 	sha1_array_clear(&parents);
 }

diff.h

@@ -13,6 +13,7 @@ struct strbuf;
 struct diff_filespec;
 struct userdiff_driver;
 struct sha1_array;
+struct commit;
 
 typedef void (*change_fn_t)(struct diff_options *options,
 		 unsigned old_mode, unsigned new_mode,
@@ -198,7 +199,7 @@ extern void show_combined_diff(struct combine_diff_path *elem, int num_parent,
 
 extern void diff_tree_combined(const unsigned char *sha1, const struct sha1_array *parents, int dense, struct rev_info *rev);
 
-extern void diff_tree_combined_merge(const unsigned char *sha1, int, struct rev_info *);
+extern void diff_tree_combined_merge(const struct commit *commit, int dense, struct rev_info *rev);
 
 void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b);
 

log-tree.c

@@ -599,9 +599,7 @@ int log_tree_diff_flush(struct rev_info *opt)
 
 static int do_diff_combined(struct rev_info *opt, struct commit *commit)
 {
-	unsigned const char *sha1 = commit->object.sha1;
-
-	diff_tree_combined_merge(sha1, opt->dense_combined_merges, opt);
+	diff_tree_combined_merge(commit, opt->dense_combined_merges, opt);
 	return !opt->loginfo;
 }