write_tree: use shared buffer for writing trees

The function to write trees allocates a new buffer for each tree.
This causes problems with performance when performing a lot
of actions involving writing trees, e.g. when doing many merges.
Fix the issue by instead handing in a shared buffer, which is then
re-used across the calls without having to re-allocate between
calls.

1 files changed, 13 insertions, 0 deletions

diff --git a/include/git2/tree.h b/include/git2/tree.h
index 2e4735c4b..a38215f9f 100644
--- a/include/git2/tree.h
+++ b/include/git2/tree.h
@@ -375,6 +375,19 @@ GIT_EXTERN(void) git_treebuilder_filter(
 GIT_EXTERN(int) git_treebuilder_write(
 	git_oid *id, git_treebuilder *bld);
 
+/**
+ * Write the contents of the tree builder as a tree object
+ * using a shared git_buf.
+ *
+ * @see git_treebuilder_write
+ *
+ * @param id Pointer to store the OID of the newly written tree
+ * @param bld Tree builder to write
+ * @param tree Shared buffer for writing the tree. Will be grown as necessary.
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_treebuilder_write_with_buffer(
+	git_oid *oid, git_treebuilder *bld, git_buf *tree);
 
 /** Callback for the tree traversal method */
 typedef int (*git_treewalk_cb)(