1 files changed, 432 insertions, 0 deletions
diff --git a/src/libgit2/merge_driver.c b/src/libgit2/merge_driver.c
new file mode 100644
index 000000000..19b35ac0e
--- /dev/null
+++ b/src/libgit2/merge_driver.c
@@ -0,0 +1,432 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "merge_driver.h"
+
+#include "vector.h"
+#include "runtime.h"
+#include "merge.h"
+#include "git2/merge.h"
+#include "git2/sys/merge.h"
+
+static const char *merge_driver_name__text = "text";
+static const char *merge_driver_name__union = "union";
+static const char *merge_driver_name__binary = "binary";
+
+struct merge_driver_registry {
+	git_rwlock lock;
+	git_vector drivers;
+};
+
+typedef struct {
+	git_merge_driver *driver;
+	int initialized;
+	char name[GIT_FLEX_ARRAY];
+} git_merge_driver_entry;
+
+static struct merge_driver_registry merge_driver_registry;
+
+static void git_merge_driver_global_shutdown(void);
+
+git_repository *git_merge_driver_source_repo(
+	const git_merge_driver_source *src)
+{
+	GIT_ASSERT_ARG_WITH_RETVAL(src, NULL);
+	return src->repo;
+}
+
+const git_index_entry *git_merge_driver_source_ancestor(
+	const git_merge_driver_source *src)
+{
+	GIT_ASSERT_ARG_WITH_RETVAL(src, NULL);
+	return src->ancestor;
+}
+
+const git_index_entry *git_merge_driver_source_ours(
+	const git_merge_driver_source *src)
+{
+	GIT_ASSERT_ARG_WITH_RETVAL(src, NULL);
+	return src->ours;
+}
+
+const git_index_entry *git_merge_driver_source_theirs(
+	const git_merge_driver_source *src)
+{
+	GIT_ASSERT_ARG_WITH_RETVAL(src, NULL);
+	return src->theirs;
+}
+
+const git_merge_file_options *git_merge_driver_source_file_options(
+	const git_merge_driver_source *src)
+{
+	GIT_ASSERT_ARG_WITH_RETVAL(src, NULL);
+	return src->file_opts;
+}
+
+int git_merge_driver__builtin_apply(
+	git_merge_driver *self,
+	const char **path_out,
+	uint32_t *mode_out,
+	git_buf *merged_out,
+	const char *filter_name,
+	const git_merge_driver_source *src)
+{
+	git_merge_driver__builtin *driver = (git_merge_driver__builtin *)self;
+	git_merge_file_options file_opts = GIT_MERGE_FILE_OPTIONS_INIT;
+	git_merge_file_result result = {0};
+	int error;
+
+	GIT_UNUSED(filter_name);
+
+	if (src->file_opts)
+		memcpy(&file_opts, src->file_opts, sizeof(git_merge_file_options));
+
+	if (driver->favor)
+		file_opts.favor = driver->favor;
+
+	if ((error = git_merge_file_from_index(&result, src->repo,
+		src->ancestor, src->ours, src->theirs, &file_opts)) < 0)
+		goto done;
+
+	if (!result.automergeable &&
+		!(file_opts.flags & GIT_MERGE_FILE_ACCEPT_CONFLICTS)) {
+		error = GIT_EMERGECONFLICT;
+		goto done;
+	}
+
+	*path_out = git_merge_file__best_path(
+		src->ancestor ? src->ancestor->path : NULL,
+		src->ours ? src->ours->path : NULL,
+		src->theirs ? src->theirs->path : NULL);
+
+	*mode_out = git_merge_file__best_mode(
+		src->ancestor ? src->ancestor->mode : 0,
+		src->ours ? src->ours->mode : 0,
+		src->theirs ? src->theirs->mode : 0);
+
+	merged_out->ptr = (char *)result.ptr;
+	merged_out->size = result.len;
+	merged_out->reserved = 0;
+	result.ptr = NULL;
+
+done:
+	git_merge_file_result_free(&result);
+	return error;
+}
+
+static int merge_driver_binary_apply(
+	git_merge_driver *self,
+	const char **path_out,
+	uint32_t *mode_out,
+	git_buf *merged_out,
+	const char *filter_name,
+	const git_merge_driver_source *src)
+{
+	GIT_UNUSED(self);
+	GIT_UNUSED(path_out);
+	GIT_UNUSED(mode_out);
+	GIT_UNUSED(merged_out);
+	GIT_UNUSED(filter_name);
+	GIT_UNUSED(src);
+
+	return GIT_EMERGECONFLICT;
+}
+
+static int merge_driver_entry_cmp(const void *a, const void *b)
+{
+	const git_merge_driver_entry *entry_a = a;
+	const git_merge_driver_entry *entry_b = b;
+
+	return strcmp(entry_a->name, entry_b->name);
+}
+
+static int merge_driver_entry_search(const void *a, const void *b)
+{
+	const char *name_a = a;
+	const git_merge_driver_entry *entry_b = b;
+
+	return strcmp(name_a, entry_b->name);
+}
+
+git_merge_driver__builtin git_merge_driver__text = {
+	{
+		GIT_MERGE_DRIVER_VERSION,
+		NULL,
+		NULL,
+		git_merge_driver__builtin_apply,
+	},
+	GIT_MERGE_FILE_FAVOR_NORMAL
+};
+
+git_merge_driver__builtin git_merge_driver__union = {
+	{
+		GIT_MERGE_DRIVER_VERSION,
+		NULL,
+		NULL,
+		git_merge_driver__builtin_apply,
+	},
+	GIT_MERGE_FILE_FAVOR_UNION
+};
+
+git_merge_driver git_merge_driver__binary = {
+	GIT_MERGE_DRIVER_VERSION,
+	NULL,
+	NULL,
+	merge_driver_binary_apply
+};
+
+/* Note: callers must lock the registry before calling this function */
+static int merge_driver_registry_insert(
+	const char *name, git_merge_driver *driver)
+{
+	git_merge_driver_entry *entry;
+
+	entry = git__calloc(1, sizeof(git_merge_driver_entry) + strlen(name) + 1);
+	GIT_ERROR_CHECK_ALLOC(entry);
+
+	strcpy(entry->name, name);
+	entry->driver = driver;
+
+	return git_vector_insert_sorted(
+		&merge_driver_registry.drivers, entry, NULL);
+}
+
+int git_merge_driver_global_init(void)
+{
+	int error;
+
+	if (git_rwlock_init(&merge_driver_registry.lock) < 0)
+		return -1;
+
+	if ((error = git_vector_init(&merge_driver_registry.drivers, 3,
+		merge_driver_entry_cmp)) < 0)
+		goto done;
+
+	if ((error = merge_driver_registry_insert(
+			merge_driver_name__text, &git_merge_driver__text.base)) < 0 ||
+		(error = merge_driver_registry_insert(
+			merge_driver_name__union, &git_merge_driver__union.base)) < 0 ||
+		(error = merge_driver_registry_insert(
+			merge_driver_name__binary, &git_merge_driver__binary)) < 0)
+		goto done;
+
+	error = git_runtime_shutdown_register(git_merge_driver_global_shutdown);
+
+done:
+	if (error < 0)
+		git_vector_free_deep(&merge_driver_registry.drivers);
+
+	return error;
+}
+
+static void git_merge_driver_global_shutdown(void)
+{
+	git_merge_driver_entry *entry;
+	size_t i;
+
+	if (git_rwlock_wrlock(&merge_driver_registry.lock) < 0)
+		return;
+
+	git_vector_foreach(&merge_driver_registry.drivers, i, entry) {
+		if (entry->driver->shutdown)
+			entry->driver->shutdown(entry->driver);
+
+		git__free(entry);
+	}
+
+	git_vector_free(&merge_driver_registry.drivers);
+
+	git_rwlock_wrunlock(&merge_driver_registry.lock);
+	git_rwlock_free(&merge_driver_registry.lock);
+}
+
+/* Note: callers must lock the registry before calling this function */
+static int merge_driver_registry_find(size_t *pos, const char *name)
+{
+	return git_vector_search2(pos, &merge_driver_registry.drivers,
+		merge_driver_entry_search, name);
+}
+
+/* Note: callers must lock the registry before calling this function */
+static git_merge_driver_entry *merge_driver_registry_lookup(
+	size_t *pos, const char *name)
+{
+	git_merge_driver_entry *entry = NULL;
+
+	if (!merge_driver_registry_find(pos, name))
+		entry = git_vector_get(&merge_driver_registry.drivers, *pos);
+
+	return entry;
+}
+
+int git_merge_driver_register(const char *name, git_merge_driver *driver)
+{
+	int error;
+
+	GIT_ASSERT_ARG(name);
+	GIT_ASSERT_ARG(driver);
+
+	if (git_rwlock_wrlock(&merge_driver_registry.lock) < 0) {
+		git_error_set(GIT_ERROR_OS, "failed to lock merge driver registry");
+		return -1;
+	}
+
+	if (!merge_driver_registry_find(NULL, name)) {
+		git_error_set(GIT_ERROR_MERGE, "attempt to reregister existing driver '%s'",
+			name);
+		error = GIT_EEXISTS;
+		goto done;
+	}
+
+	error = merge_driver_registry_insert(name, driver);
+
+done:
+	git_rwlock_wrunlock(&merge_driver_registry.lock);
+	return error;
+}
+
+int git_merge_driver_unregister(const char *name)
+{
+	git_merge_driver_entry *entry;
+	size_t pos;
+	int error = 0;
+
+	if (git_rwlock_wrlock(&merge_driver_registry.lock) < 0) {
+		git_error_set(GIT_ERROR_OS, "failed to lock merge driver registry");
+		return -1;
+	}
+
+	if ((entry = merge_driver_registry_lookup(&pos, name)) == NULL) {
+		git_error_set(GIT_ERROR_MERGE, "cannot find merge driver '%s' to unregister",
+			name);
+		error = GIT_ENOTFOUND;
+		goto done;
+	}
+
+	git_vector_remove(&merge_driver_registry.drivers, pos);
+
+	if (entry->initialized && entry->driver->shutdown) {
+		entry->driver->shutdown(entry->driver);
+		entry->initialized = false;
+	}
+
+	git__free(entry);
+
+done:
+	git_rwlock_wrunlock(&merge_driver_registry.lock);
+	return error;
+}
+
+git_merge_driver *git_merge_driver_lookup(const char *name)
+{
+	git_merge_driver_entry *entry;
+	size_t pos;
+	int error;
+
+	/* If we've decided the merge driver to use internally - and not
+	 * based on user configuration (in merge_driver_name_for_path)
+	 * then we can use a hardcoded name to compare instead of bothering
+	 * to take a lock and look it up in the vector.
+	 */
+	if (name == merge_driver_name__text)
+		return &git_merge_driver__text.base;
+	else if (name == merge_driver_name__binary)
+		return &git_merge_driver__binary;
+
+	if (git_rwlock_rdlock(&merge_driver_registry.lock) < 0) {
+		git_error_set(GIT_ERROR_OS, "failed to lock merge driver registry");
+		return NULL;
+	}
+
+	entry = merge_driver_registry_lookup(&pos, name);
+
+	git_rwlock_rdunlock(&merge_driver_registry.lock);
+
+	if (entry == NULL) {
+		git_error_set(GIT_ERROR_MERGE, "cannot use an unregistered filter");
+		return NULL;
+	}
+
+	if (!entry->initialized) {
+		if (entry->driver->initialize &&
+			(error = entry->driver->initialize(entry->driver)) < 0)
+			return NULL;
+
+		entry->initialized = 1;
+	}
+
+	return entry->driver;
+}
+
+static int merge_driver_name_for_path(
+	const char **out,
+	git_repository *repo,
+	const char *path,
+	const char *default_driver)
+{
+	const char *value;
+	int error;
+
+	*out = NULL;
+
+	if ((error = git_attr_get(&value, repo, 0, path, "merge")) < 0)
+		return error;
+
+	/* set: use the built-in 3-way merge driver ("text") */
+	if (GIT_ATTR_IS_TRUE(value))
+		*out = merge_driver_name__text;
+
+	/* unset: do not merge ("binary") */
+	else if (GIT_ATTR_IS_FALSE(value))
+		*out = merge_driver_name__binary;
+
+	else if (GIT_ATTR_IS_UNSPECIFIED(value) && default_driver)
+		*out = default_driver;
+
+	else if (GIT_ATTR_IS_UNSPECIFIED(value))
+		*out = merge_driver_name__text;
+
+	else
+		*out = value;
+
+	return 0;
+}
+
+
+GIT_INLINE(git_merge_driver *) merge_driver_lookup_with_wildcard(
+	const char *name)
+{
+	git_merge_driver *driver = git_merge_driver_lookup(name);
+
+	if (driver == NULL)
+		driver = git_merge_driver_lookup("*");
+
+	return driver;
+}
+
+int git_merge_driver_for_source(
+	const char **name_out,
+	git_merge_driver **driver_out,
+	const git_merge_driver_source *src)
+{
+	const char *path, *driver_name;
+	int error = 0;
+
+	path = git_merge_file__best_path(
+		src->ancestor ? src->ancestor->path : NULL,
+		src->ours ? src->ours->path : NULL,
+		src->theirs ? src->theirs->path : NULL);
+
+	if ((error = merge_driver_name_for_path(
+			&driver_name, src->repo, path, src->default_driver)) < 0)
+		return error;
+
+	*name_out = driver_name;
+	*driver_out = merge_driver_lookup_with_wildcard(driver_name);
+	return error;
+}
+