merge-recursive.c: Add more generic merge_recursive_generic()

merge_recursive_generic() takes, in comparison to to merge_recursive(),
no commit ("struct commit *") arguments but SHA ids ("unsigned char *"),
and no commit list of bases but an array of refs ("const char **").

This makes it more generic in the case that it can also take the SHA
of a tree to merge trees without commits, for the bases, the head
and the remote.

merge_recursive_generic() also handles locking and updating of the
index, which is a common use case of merge_recursive().

This patch also rewrites builtin-merge-recursive.c to make use of
merge_recursive_generic().  By doing this, I stumbled over the
limitation of 20 bases and I've added a warning if this limitation
is exceeded.

This patch qualifies make_virtual_commit() as static again because
this function is not needed anymore outside merge-recursive.c.

Signed-off-by: Stephan Beyer <s-beyer@gmx.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/merge-recursive.h b/merge-recursive.h
index 73e4413a80..4dd6476af6 100644
--- a/merge-recursive.h
+++ b/merge-recursive.h
@@ -14,7 +14,9 @@ int merge_trees(struct tree *head,
 		const char *branch1,
 		const char *branch2,
 		struct tree **result);
-struct commit *make_virtual_commit(struct tree *tree, const char *comment);
+extern int merge_recursive_generic(const char **base_list,
+		const unsigned char *head_sha1, const char *head_name,
+		const unsigned char *next_sha1, const char *next_name);
 int merge_recursive_config(const char *var, const char *value, void *cb);
 void merge_recursive_setup(int is_subtree_merge);
 struct tree *write_tree_from_memory(void);