Introduce 'section' as canonical spelling for 'repo.group'

The 'repo.' prefix should be reserved for repo-specific options, but
the option 'repo.group' must still be honored to stay backwards
compatible.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

shared.c

@@ -53,7 +53,7 @@ struct cgit_repo *cgit_add_repo(const char *url)
 	ret->path = NULL;
 	ret->desc = "[no description]";
 	ret->owner = NULL;
-	ret->group = ctx.cfg.repo_group;
+	ret->section = ctx.cfg.section;
 	ret->defbranch = "master";
 	ret->snapshots = ctx.cfg.snapshots;
 	ret->enable_log_filecount = ctx.cfg.enable_log_filecount;