merge-ort: copy a few small helper functions from merge-recursive.c

In a subsequent commit, we will implement the traditional recursiveness
that gave merge-recursive its name, namely merging non-unique
merge-bases to come up with a single virtual merge base.  Copy a few
helper functions from merge-recursive.c that we will use in the
implementation.

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

merge-ort.c

@@ -17,8 +17,10 @@
 #include "cache.h"
 #include "merge-ort.h"
 
+#include "alloc.h"
 #include "blob.h"
 #include "cache-tree.h"
+#include "commit.h"
 #include "commit-reach.h"
 #include "diff.h"
 #include "diffcore.h"
@@ -1348,6 +1350,24 @@ void merge_finalize(struct merge_options *opt,
 
 /*** Function Grouping: helper functions for merge_incore_*() ***/
 
+static inline void set_commit_tree(struct commit *c, struct tree *t)
+{
+	c->maybe_tree = t;
+}
+
+MAYBE_UNUSED
+static struct commit *make_virtual_commit(struct repository *repo,
+					  struct tree *tree,
+					  const char *comment)
+{
+	struct commit *commit = alloc_commit_node(repo);
+
+	set_merge_remote_desc(commit, comment, (struct object *)commit);
+	set_commit_tree(commit, tree);
+	commit->object.parsed = 1;
+	return commit;
+}
+
 static void merge_start(struct merge_options *opt, struct merge_result *result)
 {
 	/* Sanity checks on opt */