make alias lookup a public, procedural function

This converts git_config_alias to the public alias_lookup
function. Because of the nature of our config parser, we
still have to rely on setting static data. However, that
interface is wrapped so that you can just say

  value = alias_lookup(key);

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/cache.h b/cache.h
index fa5a9e523e..1e9c937299 100644
--- a/cache.h
+++ b/cache.h
@@ -765,4 +765,6 @@ int pathspec_match(const char **spec, char *matched, const char *filename, int s
 int report_path_error(const char *ps_matched, const char **pathspec, int prefix_offset);
 void overlay_tree_on_cache(const char *tree_name, const char *prefix);
 
+char *alias_lookup(const char *alias);
+
 #endif /* CACHE_H */