merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/merge-blobs.c

@@ -0,0 +1,101 @@
+#include "cache.h"
+#include "run-command.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
+#include "blob.h"
+#include "merge-blobs.h"
+#include "object-store.h"
+
+static int fill_mmfile_blob(mmfile_t *f, struct blob *obj)
+{
+	void *buf;
+	unsigned long size;
+	enum object_type type;
+
+	buf = read_object_file(&obj->object.oid, &type, &size);
+	if (!buf)
+		return -1;
+	if (type != OBJ_BLOB) {
+		free(buf);
+		return -1;
+	}
+	f->ptr = buf;
+	f->size = size;
+	return 0;
+}
+
+static void free_mmfile(mmfile_t *f)
+{
+	free(f->ptr);
+}
+
+static void *three_way_filemerge(struct index_state *istate,
+				 const char *path,
+				 mmfile_t *base,
+				 mmfile_t *our,
+				 mmfile_t *their,
+				 unsigned long *size)
+{
+	int merge_status;
+	mmbuffer_t res;
+
+	/*
+	 * This function is only used by cmd_merge_tree, which
+	 * does not respect the merge.conflictstyle option.
+	 * There is no need to worry about a label for the
+	 * common ancestor.
+	 */
+	merge_status = ll_merge(&res, path, base, NULL,
+				our, ".our", their, ".their",
+				istate, NULL);
+	if (merge_status < 0)
+		return NULL;
+
+	*size = res.size;
+	return res.ptr;
+}
+
+void *merge_blobs(struct index_state *istate, const char *path,
+		  struct blob *base, struct blob *our,
+		  struct blob *their, unsigned long *size)
+{
+	void *res = NULL;
+	mmfile_t f1, f2, common;
+
+	/*
+	 * Removed in either branch?
+	 *
+	 * NOTE! This depends on the caller having done the
+	 * proper warning about removing a file that got
+	 * modified in the other branch!
+	 */
+	if (!our || !their) {
+		enum object_type type;
+		if (base)
+			return NULL;
+		if (!our)
+			our = their;
+		return read_object_file(&our->object.oid, &type, size);
+	}
+
+	if (fill_mmfile_blob(&f1, our) < 0)
+		goto out_no_mmfile;
+	if (fill_mmfile_blob(&f2, their) < 0)
+		goto out_free_f1;
+
+	if (base) {
+		if (fill_mmfile_blob(&common, base) < 0)
+			goto out_free_f2_f1;
+	} else {
+		common.ptr = xstrdup("");
+		common.size = 0;
+	}
+	res = three_way_filemerge(istate, path, &common, &f1, &f2, size);
+	free_mmfile(&common);
+out_free_f2_f1:
+	free_mmfile(&f2);
+out_free_f1:
+	free_mmfile(&f1);
+out_no_mmfile:
+	return res;
+}