Introduce git_revert to revert a single commit

1 files changed, 217 insertions, 0 deletions

diff --git a/src/revert.c b/src/revert.c
new file mode 100644
index 000000000..34ba343b6
--- /dev/null
+++ b/src/revert.c
@@ -0,0 +1,217 @@
+/*
+* 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 "common.h"
+#include "repository.h"
+#include "filebuf.h"
+#include "merge.h"
+#include "revert.h"
+
+#include "git2/types.h"
+#include "git2/merge.h"
+#include "git2/revert.h"
+#include "git2/commit.h"
+#include "git2/sys/commit.h"
+
+#define GIT_REVERT_FILE_MODE		0666
+
+static int write_revert_head(
+	git_repository *repo,
+	const git_commit *commit,
+	const char *commit_oidstr)
+{
+	git_filebuf file = GIT_FILEBUF_INIT;
+	git_buf file_path = GIT_BUF_INIT;
+	int error = 0;
+
+	assert(repo && commit);
+
+	if ((error = git_buf_joinpath(&file_path, repo->path_repository, GIT_REVERT_HEAD_FILE)) >= 0 &&
+		(error = git_filebuf_open(&file, file_path.ptr, GIT_FILEBUF_FORCE, GIT_REVERT_FILE_MODE)) >= 0 &&
+		(error = git_filebuf_printf(&file, "%s\n", commit_oidstr)) >= 0)
+		error = git_filebuf_commit(&file);
+
+	if (error < 0)
+		git_filebuf_cleanup(&file);
+
+	git_buf_free(&file_path);
+
+	return error;
+}
+
+static int write_merge_msg(
+	git_repository *repo,
+	const git_commit *commit,
+	const char *commit_oidstr,
+	const char *commit_msgline)
+{
+	git_filebuf file = GIT_FILEBUF_INIT;
+	git_buf file_path = GIT_BUF_INIT;
+	int error = 0;
+
+	assert(repo && commit);
+
+	if ((error = git_buf_joinpath(&file_path, repo->path_repository, GIT_MERGE_MSG_FILE)) < 0 ||
+		(error = git_filebuf_open(&file, file_path.ptr, GIT_FILEBUF_FORCE, GIT_REVERT_FILE_MODE)) < 0 ||
+		(error = git_filebuf_printf(&file, "Revert \"%s\"\n\nThis reverts commit %s.\n",
+		commit_msgline, commit_oidstr)) < 0)
+		goto cleanup;
+
+	error = git_filebuf_commit(&file);
+
+cleanup:
+	if (error < 0)
+		git_filebuf_cleanup(&file);
+
+	git_buf_free(&file_path);
+
+	return error;
+}
+
+static int revert_normalize_opts(
+	git_repository *repo,
+	git_revert_opts *opts,
+	const git_revert_opts *given,
+	const char *their_label)
+{
+	int error = 0;
+	unsigned int default_checkout_strategy = GIT_CHECKOUT_SAFE_CREATE |
+		GIT_CHECKOUT_ALLOW_CONFLICTS;
+
+	GIT_UNUSED(repo);
+
+	if (given != NULL)
+		memcpy(opts, given, sizeof(git_revert_opts));
+	else {
+		git_revert_opts default_opts = GIT_REVERT_OPTS_INIT;
+		memcpy(opts, &default_opts, sizeof(git_revert_opts));
+	}
+
+	if (!opts->checkout_opts.checkout_strategy)
+		opts->checkout_opts.checkout_strategy = default_checkout_strategy;
+
+	if (!opts->checkout_opts.our_label)
+		opts->checkout_opts.our_label = "HEAD";
+
+	if (!opts->checkout_opts.their_label)
+		opts->checkout_opts.their_label = their_label;
+
+	return error;
+}
+
+int git_revert(
+	git_repository *repo,
+	git_commit *commit,
+	const git_revert_opts *given_opts)
+{
+	git_revert_opts opts;
+	git_commit *parent_commit = NULL;
+	git_tree *parent_tree = NULL, *our_tree = NULL, *revert_tree = NULL;
+	git_index *index_new = NULL, *index_repo = NULL;
+	char commit_oidstr[GIT_OID_HEXSZ + 1];
+	const char *commit_msg;
+	git_buf their_label = GIT_BUF_INIT;
+	int parent = 0;
+	int error = 0;
+
+	assert(repo && commit);
+
+	if ((error = git_repository__ensure_not_bare(repo, "revert")) < 0)
+		return error;
+
+	git_oid_fmt(commit_oidstr, git_commit_id(commit));
+	commit_oidstr[GIT_OID_HEXSZ] = '\0';
+
+	if ((commit_msg = git_commit_summary(commit)) == NULL) {
+		error = -1;
+		goto on_error;
+	}
+
+	if ((error = git_buf_printf(&their_label, "parent of %.7s... %s", commit_oidstr, commit_msg)) < 0 ||
+		(error = revert_normalize_opts(repo, &opts, given_opts, git_buf_cstr(&their_label))) < 0 ||
+		(error = write_revert_head(repo, commit, commit_oidstr)) < 0 ||
+		(error = write_merge_msg(repo, commit, commit_oidstr, commit_msg)) < 0 ||
+		(error = git_repository_head_tree(&our_tree, repo)) < 0 ||
+		(error = git_commit_tree(&revert_tree, commit)) < 0)
+		goto on_error;
+
+	if (git_commit_parentcount(commit) > 1) {
+		if (!opts.mainline) {
+			giterr_set(GITERR_REVERT,
+				"Mainline branch is not specified but %s is a merge commit",
+				commit_oidstr);
+			error = -1;
+			goto on_error;
+		}
+
+		parent = opts.mainline;
+	} else {
+		if (opts.mainline) {
+			giterr_set(GITERR_REVERT,
+				"Mainline branch was specified but %s is not a merge",
+				commit_oidstr);
+			error = -1;
+			goto on_error;
+		}
+
+		parent = git_commit_parentcount(commit);
+	}
+
+	if (parent &&
+		((error = git_commit_parent(&parent_commit, commit, (parent - 1))) < 0 ||
+		(error = git_commit_tree(&parent_tree, parent_commit)) < 0))
+		goto on_error;
+
+	if ((error = git_merge_trees(&index_new, repo, revert_tree, our_tree, parent_tree, &opts.merge_tree_opts)) < 0 ||
+		(error = git_merge__indexes(repo, index_new)) < 0 ||
+		(error = git_repository_index(&index_repo, repo)) < 0 ||
+		(error = git_checkout_index(repo, index_repo, &opts.checkout_opts)) < 0)
+		goto on_error;
+
+	goto done;
+
+on_error:
+	git_revert__cleanup(repo);
+
+done:
+	git_index_free(index_new);
+	git_index_free(index_repo);
+	git_tree_free(parent_tree);
+	git_tree_free(our_tree);
+	git_tree_free(revert_tree);
+	git_commit_free(parent_commit);
+	git_buf_free(&their_label);
+
+	return error;
+}
+
+int git_revert__cleanup(git_repository *repo)
+{
+	int error = 0;
+	git_buf revert_head_path = GIT_BUF_INIT,
+		merge_msg_path = GIT_BUF_INIT;
+
+	assert(repo);
+
+	if (git_buf_joinpath(&revert_head_path, repo->path_repository, GIT_REVERT_HEAD_FILE) < 0 ||
+		git_buf_joinpath(&merge_msg_path, repo->path_repository, GIT_MERGE_MSG_FILE) < 0)
+		return -1;
+
+	if (git_path_isfile(revert_head_path.ptr)) {
+		if ((error = p_unlink(revert_head_path.ptr)) < 0)
+			goto cleanup;
+	}
+
+	if (git_path_isfile(merge_msg_path.ptr))
+		(void)p_unlink(merge_msg_path.ptr);
+
+cleanup:
+	git_buf_free(&merge_msg_path);
+	git_buf_free(&revert_head_path);
+
+	return error;
+}