merge-ort-wrappers: new convience wrappers to mimic the old merge API

There are a few differences between the new API in merge-ort and the old
API in merge-recursive.  While the new API is more flexible, it might
feel like more work at times than the old API.  merge-ort-wrappers
creates two convenience wrappers taking the exact same arguments as the
old merge_trees() and merge_recursive() functions and implements them
via the new API.  This makes converting existing callsites easier, and
serves to highlight some of the differences in the API.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -922,6 +922,7 @@ LIB_OBJS += match-trees.o
 LIB_OBJS += mem-pool.o
 LIB_OBJS += merge-blobs.o
 LIB_OBJS += merge-ort.o
+LIB_OBJS += merge-ort-wrappers.o
 LIB_OBJS += merge-recursive.o
 LIB_OBJS += merge.o
 LIB_OBJS += mergesort.o

merge-ort-wrappers.c

@@ -0,0 +1,62 @@
+#include "cache.h"
+#include "merge-ort.h"
+#include "merge-ort-wrappers.h"
+
+#include "commit.h"
+
+static int unclean(struct merge_options *opt, struct tree *head)
+{
+	/* Sanity check on repo state; index must match head */
+	struct strbuf sb = STRBUF_INIT;
+
+	if (head && repo_index_has_changes(opt->repo, head, &sb)) {
+		fprintf(stderr, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
+		    sb.buf);
+		strbuf_release(&sb);
+		return -1;
+	}
+
+	return 0;
+}
+
+int merge_ort_nonrecursive(struct merge_options *opt,
+			   struct tree *head,
+			   struct tree *merge,
+			   struct tree *merge_base)
+{
+	struct merge_result result;
+
+	if (unclean(opt, head))
+		return -1;
+
+	if (oideq(&merge_base->object.oid, &merge->object.oid)) {
+		printf(_("Already up to date!"));
+		return 1;
+	}
+
+	memset(&result, 0, sizeof(result));
+	merge_incore_nonrecursive(opt, merge_base, head, merge, &result);
+	merge_switch_to_result(opt, head, &result, 1, 1);
+
+	return result.clean;
+}
+
+int merge_ort_recursive(struct merge_options *opt,
+			struct commit *side1,
+			struct commit *side2,
+			struct commit_list *merge_bases,
+			struct commit **result)
+{
+	struct tree *head = repo_get_commit_tree(opt->repo, side1);
+	struct merge_result tmp;
+
+	if (unclean(opt, head))
+		return -1;
+
+	memset(&tmp, 0, sizeof(tmp));
+	merge_incore_recursive(opt, merge_bases, side1, side2, &tmp);
+	merge_switch_to_result(opt, head, &tmp, 1, 1);
+	*result = NULL;
+
+	return tmp.clean;
+}

merge-ort-wrappers.h

@@ -0,0 +1,25 @@
+#ifndef MERGE_ORT_WRAPPERS_H
+#define MERGE_ORT_WRAPPERS_H
+
+#include "merge-recursive.h"
+
+/*
+ * rename-detecting three-way merge, no recursion.
+ * Wrapper mimicking the old merge_trees() function.
+ */
+int merge_ort_nonrecursive(struct merge_options *opt,
+			   struct tree *head,
+			   struct tree *merge,
+			   struct tree *common);
+
+/*
+ * rename-detecting three-way merge with recursive ancestor consolidation.
+ * Wrapper mimicking the old merge_recursive() function.
+ */
+int merge_ort_recursive(struct merge_options *opt,
+			struct commit *h1,
+			struct commit *h2,
+			struct commit_list *ancestors,
+			struct commit **result);
+
+#endif