ui-tree: allow per repository override for enable-blame

The blame operation can cause high cost in terms of CPU load for huge
repositories. Let's add a per repository override for enable-blame.

Signed-off-by: Christian Hesse <mail@eworm.de>
diff --git a/ui-tree.c b/ui-tree.c
index 4be89c8..84eb17d 100644
--- a/ui-tree.c
+++ b/ui-tree.c
@@ -110,7 +110,7 @@
 	htmlf("blob: %s (", oid_to_hex(oid));
 	cgit_plain_link("plain", NULL, NULL, ctx.qry.head,
 		        rev, path);
-	if (ctx.cfg.enable_blame) {
+	if (ctx.repo->enable_blame) {
 		html(") (");
 		cgit_blame_link("blame", NULL, NULL, ctx.qry.head,
 			        rev, path);
@@ -251,7 +251,7 @@
 	if (!S_ISGITLINK(mode))
 		cgit_plain_link("plain", NULL, "button", ctx.qry.head,
 				walk_tree_ctx->curr_rev, fullpath.buf);
-	if (!S_ISDIR(mode) && ctx.cfg.enable_blame)
+	if (!S_ISDIR(mode) && ctx.repo->enable_blame)
 		cgit_blame_link("blame", NULL, "button", ctx.qry.head,
 				walk_tree_ctx->curr_rev, fullpath.buf);
 	html("</td></tr>\n");