Create a commit and write it into a buffer
Create a commit as with git_commit_create() but instead of
writing it to the objectdb, write the contents of the object into a
buffer.
The encoding for the message in the commit, represented with a standard encoding name. E.g. "UTF-8". If NULL, no encoding header is written and UTF-8 is assumed.
Full message for this commit
An instance of a git_tree object that will be used as the tree for the commit. This tree object must also be owned by the given repo.
Number of parents for this commit
Array of parent_count pointers to git_commit objects that will be used as the parents for this commit. This array may be NULL if parent_count is 0 (root commit). All the given commits must be owned by the repo.
0 or an error code