The eighth batch

[alt-git.git] / builtin / clone.c

/*
 * Builtin "git clone"
 *
 * Copyright (c) 2007 Kristian Høgsberg <krh@redhat.com>,
 *               2008 Daniel Barkalow <barkalow@iabervon.org>
 * Based on git-commit.sh by Junio C Hamano and Linus Torvalds
 *
 * Clone a repository into a different directory that does not yet exist.
 */

#include "builtin.h"
#include "abspath.h"
#include "advice.h"
#include "config.h"
#include "copy.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "lockfile.h"
#include "parse-options.h"
#include "refs.h"
#include "refspec.h"
#include "object-file.h"
#include "object-store-ll.h"
#include "tree.h"
#include "tree-walk.h"
#include "unpack-trees.h"
#include "transport.h"
#include "strbuf.h"
#include "dir.h"
#include "dir-iterator.h"
#include "iterator.h"
#include "sigchain.h"
#include "branch.h"
#include "remote.h"
#include "run-command.h"
#include "setup.h"
#include "connected.h"
#include "packfile.h"
#include "path.h"
#include "pkt-line.h"
#include "list-objects-filter-options.h"
#include "hook.h"
#include "bundle.h"
#include "bundle-uri.h"

/*
 * Overall FIXMEs:
 *  - respect DB_ENVIRONMENT for .git/objects.
 *
 * Implementation notes:
 *  - dropping use-separate-remote and no-separate-remote compatibility
 *
 */
static const char * const builtin_clone_usage[] = {
        N_("git clone [<options>] [--] <repo> [<dir>]"),
        NULL
};

static int option_no_checkout, option_bare, option_mirror, option_single_branch = -1;
static int option_local = -1, option_no_hardlinks, option_shared;
static int option_no_tags;
static int option_shallow_submodules;
static int option_reject_shallow = -1;    /* unspecified */
static int config_reject_shallow = -1;    /* unspecified */
static int deepen;
static char *option_template, *option_depth, *option_since;
static char *option_origin = NULL;
static char *remote_name = NULL;
static char *option_branch = NULL;
static struct string_list option_not = STRING_LIST_INIT_NODUP;
static const char *real_git_dir;
static const char *ref_format;
static char *option_upload_pack = "git-upload-pack";
static int option_verbosity;
static int option_progress = -1;
static int option_sparse_checkout;
static enum transport_family family;
static struct string_list option_config = STRING_LIST_INIT_NODUP;
static struct string_list option_required_reference = STRING_LIST_INIT_NODUP;
static struct string_list option_optional_reference = STRING_LIST_INIT_NODUP;
static int option_dissociate;
static int max_jobs = -1;
static struct string_list option_recurse_submodules = STRING_LIST_INIT_NODUP;
static struct list_objects_filter_options filter_options = LIST_OBJECTS_FILTER_INIT;
static int option_filter_submodules = -1;    /* unspecified */
static int config_filter_submodules = -1;    /* unspecified */
static struct string_list server_options = STRING_LIST_INIT_NODUP;
static int option_remote_submodules;
static const char *bundle_uri;

static int recurse_submodules_cb(const struct option *opt,
                                 const char *arg, int unset)
{
        if (unset)
                string_list_clear((struct string_list *)opt->value, 0);
        else if (arg)
                string_list_append((struct string_list *)opt->value, arg);
        else
                string_list_append((struct string_list *)opt->value,
                                   (const char *)opt->defval);

        return 0;
}

static struct option builtin_clone_options[] = {
        OPT__VERBOSITY(&option_verbosity),
        OPT_BOOL(0, "progress", &option_progress,
                 N_("force progress reporting")),
        OPT_BOOL(0, "reject-shallow", &option_reject_shallow,
                 N_("don't clone shallow repository")),
        OPT_BOOL('n', "no-checkout", &option_no_checkout,
                 N_("don't create a checkout")),
        OPT_BOOL(0, "bare", &option_bare, N_("create a bare repository")),
        OPT_HIDDEN_BOOL(0, "naked", &option_bare,
                        N_("create a bare repository")),
        OPT_BOOL(0, "mirror", &option_mirror,
                 N_("create a mirror repository (implies --bare)")),
        OPT_BOOL('l', "local", &option_local,
                N_("to clone from a local repository")),
        OPT_BOOL(0, "no-hardlinks", &option_no_hardlinks,
                    N_("don't use local hardlinks, always copy")),
        OPT_BOOL('s', "shared", &option_shared,
                    N_("setup as shared repository")),
        { OPTION_CALLBACK, 0, "recurse-submodules", &option_recurse_submodules,
          N_("pathspec"), N_("initialize submodules in the clone"),
          PARSE_OPT_OPTARG, recurse_submodules_cb, (intptr_t)"." },
        OPT_ALIAS(0, "recursive", "recurse-submodules"),
        OPT_INTEGER('j', "jobs", &max_jobs,
                    N_("number of submodules cloned in parallel")),
        OPT_STRING(0, "template", &option_template, N_("template-directory"),
                   N_("directory from which templates will be used")),
        OPT_STRING_LIST(0, "reference", &option_required_reference, N_("repo"),
                        N_("reference repository")),
        OPT_STRING_LIST(0, "reference-if-able", &option_optional_reference,
                        N_("repo"), N_("reference repository")),
        OPT_BOOL(0, "dissociate", &option_dissociate,
                 N_("use --reference only while cloning")),
        OPT_STRING('o', "origin", &option_origin, N_("name"),
                   N_("use <name> instead of 'origin' to track upstream")),
        OPT_STRING('b', "branch", &option_branch, N_("branch"),
                   N_("checkout <branch> instead of the remote's HEAD")),
        OPT_STRING('u', "upload-pack", &option_upload_pack, N_("path"),
                   N_("path to git-upload-pack on the remote")),
        OPT_STRING(0, "depth", &option_depth, N_("depth"),
                    N_("create a shallow clone of that depth")),
        OPT_STRING(0, "shallow-since", &option_since, N_("time"),
                    N_("create a shallow clone since a specific time")),
        OPT_STRING_LIST(0, "shallow-exclude", &option_not, N_("revision"),
                        N_("deepen history of shallow clone, excluding rev")),
        OPT_BOOL(0, "single-branch", &option_single_branch,
                    N_("clone only one branch, HEAD or --branch")),
        OPT_BOOL(0, "no-tags", &option_no_tags,
                 N_("don't clone any tags, and make later fetches not to follow them")),
        OPT_BOOL(0, "shallow-submodules", &option_shallow_submodules,
                    N_("any cloned submodules will be shallow")),
        OPT_STRING(0, "separate-git-dir", &real_git_dir, N_("gitdir"),
                   N_("separate git dir from working tree")),
        OPT_STRING(0, "ref-format", &ref_format, N_("format"),
                   N_("specify the reference format to use")),
        OPT_STRING_LIST('c', "config", &option_config, N_("key=value"),
                        N_("set config inside the new repository")),
        OPT_STRING_LIST(0, "server-option", &server_options,
                        N_("server-specific"), N_("option to transmit")),
        OPT_IPVERSION(&family),
        OPT_PARSE_LIST_OBJECTS_FILTER(&filter_options),
        OPT_BOOL(0, "also-filter-submodules", &option_filter_submodules,
                    N_("apply partial clone filters to submodules")),
        OPT_BOOL(0, "remote-submodules", &option_remote_submodules,
                    N_("any cloned submodules will use their remote-tracking branch")),
        OPT_BOOL(0, "sparse", &option_sparse_checkout,
                    N_("initialize sparse-checkout file to include only files at root")),
        OPT_STRING(0, "bundle-uri", &bundle_uri,
                   N_("uri"), N_("a URI for downloading bundles before fetching from origin remote")),
        OPT_END()
};

static const char *get_repo_path_1(struct strbuf *path, int *is_bundle)
{
        static char *suffix[] = { "/.git", "", ".git/.git", ".git" };
        static char *bundle_suffix[] = { ".bundle", "" };
        size_t baselen = path->len;
        struct stat st;
        int i;

        for (i = 0; i < ARRAY_SIZE(suffix); i++) {
                strbuf_setlen(path, baselen);
                strbuf_addstr(path, suffix[i]);
                if (stat(path->buf, &st))
                        continue;
                if (S_ISDIR(st.st_mode) && is_git_directory(path->buf)) {
                        *is_bundle = 0;
                        return path->buf;
                } else if (S_ISREG(st.st_mode) && st.st_size > 8) {
                        /* Is it a "gitfile"? */
                        char signature[8];
                        const char *dst;
                        int len, fd = open(path->buf, O_RDONLY);
                        if (fd < 0)
                                continue;
                        len = read_in_full(fd, signature, 8);
                        close(fd);
                        if (len != 8 || strncmp(signature, "gitdir: ", 8))
                                continue;
                        dst = read_gitfile(path->buf);
                        if (dst) {
                                *is_bundle = 0;
                                return dst;
                        }
                }
        }

        for (i = 0; i < ARRAY_SIZE(bundle_suffix); i++) {
                strbuf_setlen(path, baselen);
                strbuf_addstr(path, bundle_suffix[i]);
                if (!stat(path->buf, &st) && S_ISREG(st.st_mode)) {
                        *is_bundle = 1;
                        return path->buf;
                }
        }

        return NULL;
}

static char *get_repo_path(const char *repo, int *is_bundle)
{
        struct strbuf path = STRBUF_INIT;
        const char *raw;
        char *canon;

        strbuf_addstr(&path, repo);
        raw = get_repo_path_1(&path, is_bundle);
        canon = raw ? absolute_pathdup(raw) : NULL;
        strbuf_release(&path);
        return canon;
}

static int add_one_reference(struct string_list_item *item, void *cb_data)
{
        struct strbuf err = STRBUF_INIT;
        int *required = cb_data;
        char *ref_git = compute_alternate_path(item->string, &err);

        if (!ref_git) {
                if (*required)
                        die("%s", err.buf);
                else
                        fprintf(stderr,
                                _("info: Could not add alternate for '%s': %s\n"),
                                item->string, err.buf);
        } else {
                struct strbuf sb = STRBUF_INIT;
                strbuf_addf(&sb, "%s/objects", ref_git);
                add_to_alternates_file(sb.buf);
                strbuf_release(&sb);
        }

        strbuf_release(&err);
        free(ref_git);
        return 0;
}

static void setup_reference(void)
{
        int required = 1;
        for_each_string_list(&option_required_reference,
                             add_one_reference, &required);
        required = 0;
        for_each_string_list(&option_optional_reference,
                             add_one_reference, &required);
}

static void copy_alternates(struct strbuf *src, const char *src_repo)
{
        /*
         * Read from the source objects/info/alternates file
         * and copy the entries to corresponding file in the
         * destination repository with add_to_alternates_file().
         * Both src and dst have "$path/objects/info/alternates".
         *
         * Instead of copying bit-for-bit from the original,
         * we need to append to existing one so that the already
         * created entry via "clone -s" is not lost, and also
         * to turn entries with paths relative to the original
         * absolute, so that they can be used in the new repository.
         */
        FILE *in = xfopen(src->buf, "r");
        struct strbuf line = STRBUF_INIT;

        while (strbuf_getline(&line, in) != EOF) {
                char *abs_path;
                if (!line.len || line.buf[0] == '#')
                        continue;
                if (is_absolute_path(line.buf)) {
                        add_to_alternates_file(line.buf);
                        continue;
                }
                abs_path = mkpathdup("%s/objects/%s", src_repo, line.buf);
                if (!normalize_path_copy(abs_path, abs_path))
                        add_to_alternates_file(abs_path);
                else
                        warning("skipping invalid relative alternate: %s/%s",
                                src_repo, line.buf);
                free(abs_path);
        }
        strbuf_release(&line);
        fclose(in);
}

static void mkdir_if_missing(const char *pathname, mode_t mode)
{
        struct stat st;

        if (!mkdir(pathname, mode))
                return;

        if (errno != EEXIST)
                die_errno(_("failed to create directory '%s'"), pathname);
        else if (stat(pathname, &st))
                die_errno(_("failed to stat '%s'"), pathname);
        else if (!S_ISDIR(st.st_mode))
                die(_("%s exists and is not a directory"), pathname);
}

static void copy_or_link_directory(struct strbuf *src, struct strbuf *dest,
                                   const char *src_repo)
{
        int src_len, dest_len;
        struct dir_iterator *iter;
        int iter_status;

        /*
         * Refuse copying directories by default which aren't owned by us. The
         * code that performs either the copying or hardlinking is not prepared
         * to handle various edge cases where an adversary may for example
         * racily swap out files for symlinks. This can cause us to
         * inadvertently use the wrong source file.
         *
         * Furthermore, even if we were prepared to handle such races safely,
         * creating hardlinks across user boundaries is an inherently unsafe
         * operation as the hardlinked files can be rewritten at will by the
         * potentially-untrusted user. We thus refuse to do so by default.
         */
        die_upon_dubious_ownership(NULL, NULL, src_repo);

        mkdir_if_missing(dest->buf, 0777);

        iter = dir_iterator_begin(src->buf, DIR_ITERATOR_PEDANTIC);

        if (!iter) {
                if (errno == ENOTDIR) {
                        int saved_errno = errno;
                        struct stat st;

                        if (!lstat(src->buf, &st) && S_ISLNK(st.st_mode))
                                die(_("'%s' is a symlink, refusing to clone with --local"),
                                    src->buf);
                        errno = saved_errno;
                }
                die_errno(_("failed to start iterator over '%s'"), src->buf);
        }

        strbuf_addch(src, '/');
        src_len = src->len;
        strbuf_addch(dest, '/');
        dest_len = dest->len;

        while ((iter_status = dir_iterator_advance(iter)) == ITER_OK) {
                strbuf_setlen(src, src_len);
                strbuf_addstr(src, iter->relative_path);
                strbuf_setlen(dest, dest_len);
                strbuf_addstr(dest, iter->relative_path);

                if (S_ISLNK(iter->st.st_mode))
                        die(_("symlink '%s' exists, refusing to clone with --local"),
                            iter->relative_path);

                if (S_ISDIR(iter->st.st_mode)) {
                        mkdir_if_missing(dest->buf, 0777);
                        continue;
                }

                /* Files that cannot be copied bit-for-bit... */
                if (!fspathcmp(iter->relative_path, "info/alternates")) {
                        copy_alternates(src, src_repo);
                        continue;
                }

                if (unlink(dest->buf) && errno != ENOENT)
                        die_errno(_("failed to unlink '%s'"), dest->buf);
                if (!option_no_hardlinks) {
                        if (!link(src->buf, dest->buf)) {
                                struct stat st;

                                /*
                                 * Sanity-check whether the created hardlink
                                 * actually links to the expected file now. This
                                 * catches time-of-check-time-of-use bugs in
                                 * case the source file was meanwhile swapped.
                                 */
                                if (lstat(dest->buf, &st))
                                        die(_("hardlink cannot be checked at '%s'"), dest->buf);
                                if (st.st_mode != iter->st.st_mode ||
                                    st.st_ino != iter->st.st_ino ||
                                    st.st_dev != iter->st.st_dev ||
                                    st.st_size != iter->st.st_size ||
                                    st.st_uid != iter->st.st_uid ||
                                    st.st_gid != iter->st.st_gid)
                                        die(_("hardlink different from source at '%s'"), dest->buf);

                                continue;
                        }
                        if (option_local > 0)
                                die_errno(_("failed to create link '%s'"), dest->buf);
                        option_no_hardlinks = 1;
                }
                if (copy_file_with_time(dest->buf, src->buf, 0666))
                        die_errno(_("failed to copy file to '%s'"), dest->buf);
        }

        if (iter_status != ITER_DONE) {
                strbuf_setlen(src, src_len);
                die(_("failed to iterate over '%s'"), src->buf);
        }
}

static void clone_local(const char *src_repo, const char *dest_repo)
{
        if (option_shared) {
                struct strbuf alt = STRBUF_INIT;
                get_common_dir(&alt, src_repo);
                strbuf_addstr(&alt, "/objects");
                add_to_alternates_file(alt.buf);
                strbuf_release(&alt);
        } else {
                struct strbuf src = STRBUF_INIT;
                struct strbuf dest = STRBUF_INIT;
                get_common_dir(&src, src_repo);
                get_common_dir(&dest, dest_repo);
                strbuf_addstr(&src, "/objects");
                strbuf_addstr(&dest, "/objects");
                copy_or_link_directory(&src, &dest, src_repo);
                strbuf_release(&src);
                strbuf_release(&dest);
        }

        if (0 <= option_verbosity)
                fprintf(stderr, _("done.\n"));
}

static const char *junk_work_tree;
static int junk_work_tree_flags;
static const char *junk_git_dir;
static int junk_git_dir_flags;
static enum {
        JUNK_LEAVE_NONE,
        JUNK_LEAVE_REPO,
        JUNK_LEAVE_ALL
} junk_mode = JUNK_LEAVE_NONE;

static const char junk_leave_repo_msg[] =
N_("Clone succeeded, but checkout failed.\n"
   "You can inspect what was checked out with 'git status'\n"
   "and retry with 'git restore --source=HEAD :/'\n");

static void remove_junk(void)
{
        struct strbuf sb = STRBUF_INIT;

        switch (junk_mode) {
        case JUNK_LEAVE_REPO:
                warning("%s", _(junk_leave_repo_msg));
                /* fall-through */
        case JUNK_LEAVE_ALL:
                return;
        default:
                /* proceed to removal */
                break;
        }

        if (junk_git_dir) {
                strbuf_addstr(&sb, junk_git_dir);
                remove_dir_recursively(&sb, junk_git_dir_flags);
                strbuf_reset(&sb);
        }
        if (junk_work_tree) {
                strbuf_addstr(&sb, junk_work_tree);
                remove_dir_recursively(&sb, junk_work_tree_flags);
        }
        strbuf_release(&sb);
}

static void remove_junk_on_signal(int signo)
{
        remove_junk();
        sigchain_pop(signo);
        raise(signo);
}

static struct ref *find_remote_branch(const struct ref *refs, const char *branch)
{
        struct ref *ref;
        struct strbuf head = STRBUF_INIT;
        strbuf_addstr(&head, "refs/heads/");
        strbuf_addstr(&head, branch);
        ref = find_ref_by_name(refs, head.buf);
        strbuf_release(&head);

        if (ref)
                return ref;

        strbuf_addstr(&head, "refs/tags/");
        strbuf_addstr(&head, branch);
        ref = find_ref_by_name(refs, head.buf);
        strbuf_release(&head);

        return ref;
}

static struct ref *wanted_peer_refs(const struct ref *refs,
                struct refspec *refspec)
{
        struct ref *head = copy_ref(find_ref_by_name(refs, "HEAD"));
        struct ref *local_refs = head;
        struct ref **tail = head ? &head->next : &local_refs;

        if (option_single_branch) {
                struct ref *remote_head = NULL;

                if (!option_branch)
                        remote_head = guess_remote_head(head, refs, 0);
                else {
                        local_refs = NULL;
                        tail = &local_refs;
                        remote_head = copy_ref(find_remote_branch(refs, option_branch));
                }

                if (!remote_head && option_branch)
                        warning(_("Could not find remote branch %s to clone."),
                                option_branch);
                else {
                        int i;
                        for (i = 0; i < refspec->nr; i++)
                                get_fetch_map(remote_head, &refspec->items[i],
                                              &tail, 0);

                        /* if --branch=tag, pull the requested tag explicitly */
                        get_fetch_map(remote_head, tag_refspec, &tail, 0);
                }
                free_refs(remote_head);
        } else {
                int i;
                for (i = 0; i < refspec->nr; i++)
                        get_fetch_map(refs, &refspec->items[i], &tail, 0);
        }

        if (!option_mirror && !option_single_branch && !option_no_tags)
                get_fetch_map(refs, tag_refspec, &tail, 0);

        return local_refs;
}

static void write_remote_refs(const struct ref *local_refs)
{
        const struct ref *r;

        struct ref_transaction *t;
        struct strbuf err = STRBUF_INIT;

        t = ref_store_transaction_begin(get_main_ref_store(the_repository),
                                        &err);
        if (!t)
                die("%s", err.buf);

        for (r = local_refs; r; r = r->next) {
                if (!r->peer_ref)
                        continue;
                if (ref_transaction_create(t, r->peer_ref->name, &r->old_oid,
                                           0, NULL, &err))
                        die("%s", err.buf);
        }

        if (initial_ref_transaction_commit(t, &err))
                die("%s", err.buf);

        strbuf_release(&err);
        ref_transaction_free(t);
}

static void write_followtags(const struct ref *refs, const char *msg)
{
        const struct ref *ref;
        for (ref = refs; ref; ref = ref->next) {
                if (!starts_with(ref->name, "refs/tags/"))
                        continue;
                if (ends_with(ref->name, "^{}"))
                        continue;
                if (!repo_has_object_file_with_flags(the_repository, &ref->old_oid,
                                                     OBJECT_INFO_QUICK |
                                                     OBJECT_INFO_SKIP_FETCH_OBJECT))
                        continue;
                refs_update_ref(get_main_ref_store(the_repository), msg,
                                ref->name, &ref->old_oid, NULL, 0,
                                UPDATE_REFS_DIE_ON_ERR);
        }
}

static const struct object_id *iterate_ref_map(void *cb_data)
{
        struct ref **rm = cb_data;
        struct ref *ref = *rm;

        /*
         * Skip anything missing a peer_ref, which we are not
         * actually going to write a ref for.
         */
        while (ref && !ref->peer_ref)
                ref = ref->next;
        if (!ref)
                return NULL;

        *rm = ref->next;
        return &ref->old_oid;
}

static void update_remote_refs(const struct ref *refs,
                               const struct ref *mapped_refs,
                               const struct ref *remote_head_points_at,
                               const char *branch_top,
                               const char *msg,
                               struct transport *transport,
                               int check_connectivity)
{
        const struct ref *rm = mapped_refs;

        if (check_connectivity) {
                struct check_connected_options opt = CHECK_CONNECTED_INIT;

                opt.transport = transport;
                opt.progress = transport->progress;

                if (check_connected(iterate_ref_map, &rm, &opt))
                        die(_("remote did not send all necessary objects"));
        }

        if (refs) {
                write_remote_refs(mapped_refs);
                if (option_single_branch && !option_no_tags)
                        write_followtags(refs, msg);
        }

        if (remote_head_points_at && !option_bare) {
                struct strbuf head_ref = STRBUF_INIT;
                strbuf_addstr(&head_ref, branch_top);
                strbuf_addstr(&head_ref, "HEAD");
                if (refs_update_symref(get_main_ref_store(the_repository), head_ref.buf,
                                       remote_head_points_at->peer_ref->name,
                                       msg) < 0)
                        die(_("unable to update %s"), head_ref.buf);
                strbuf_release(&head_ref);
        }
}

static void update_head(const struct ref *our, const struct ref *remote,
                        const char *unborn, const char *msg)
{
        const char *head;
        if (our && skip_prefix(our->name, "refs/heads/", &head)) {
                /* Local default branch link */
                if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", our->name, NULL) < 0)
                        die(_("unable to update HEAD"));
                if (!option_bare) {
                        refs_update_ref(get_main_ref_store(the_repository),
                                        msg, "HEAD", &our->old_oid, NULL, 0,
                                        UPDATE_REFS_DIE_ON_ERR);
                        install_branch_config(0, head, remote_name, our->name);
                }
        } else if (our) {
                struct commit *c = lookup_commit_reference(the_repository,
                                                           &our->old_oid);
                /* --branch specifies a non-branch (i.e. tags), detach HEAD */
                refs_update_ref(get_main_ref_store(the_repository), msg,
                                "HEAD", &c->object.oid, NULL, REF_NO_DEREF,
                                UPDATE_REFS_DIE_ON_ERR);
        } else if (remote) {
                /*
                 * We know remote HEAD points to a non-branch, or
                 * HEAD points to a branch but we don't know which one.
                 * Detach HEAD in all these cases.
                 */
                refs_update_ref(get_main_ref_store(the_repository), msg,
                                "HEAD", &remote->old_oid, NULL, REF_NO_DEREF,
                                UPDATE_REFS_DIE_ON_ERR);
        } else if (unborn && skip_prefix(unborn, "refs/heads/", &head)) {
                /*
                 * Unborn head from remote; same as "our" case above except
                 * that we have no ref to update.
                 */
                if (refs_update_symref(get_main_ref_store(the_repository), "HEAD", unborn, NULL) < 0)
                        die(_("unable to update HEAD"));
                if (!option_bare)
                        install_branch_config(0, head, remote_name, unborn);
        }
}

static int git_sparse_checkout_init(const char *repo)
{
        struct child_process cmd = CHILD_PROCESS_INIT;
        int result = 0;
        strvec_pushl(&cmd.args, "-C", repo, "sparse-checkout", "set", NULL);

        /*
         * We must apply the setting in the current process
         * for the later checkout to use the sparse-checkout file.
         */
        core_apply_sparse_checkout = 1;

        cmd.git_cmd = 1;
        if (run_command(&cmd)) {
                error(_("failed to initialize sparse-checkout"));
                result = 1;
        }

        return result;
}

static int checkout(int submodule_progress, int filter_submodules)
{
        struct object_id oid;
        char *head;
        struct lock_file lock_file = LOCK_INIT;
        struct unpack_trees_options opts;
        struct tree *tree;
        struct tree_desc t;
        int err = 0;

        if (option_no_checkout)
                return 0;

        head = refs_resolve_refdup(get_main_ref_store(the_repository), "HEAD",
                                   RESOLVE_REF_READING, &oid, NULL);
        if (!head) {
                warning(_("remote HEAD refers to nonexistent ref, "
                          "unable to checkout"));
                return 0;
        }
        if (!strcmp(head, "HEAD")) {
                if (advice_enabled(ADVICE_DETACHED_HEAD))
                        detach_advice(oid_to_hex(&oid));
                FREE_AND_NULL(head);
        } else {
                if (!starts_with(head, "refs/heads/"))
                        die(_("HEAD not found below refs/heads!"));
        }

        /* We need to be in the new work tree for the checkout */
        setup_work_tree();

        repo_hold_locked_index(the_repository, &lock_file, LOCK_DIE_ON_ERROR);

        memset(&opts, 0, sizeof opts);
        opts.update = 1;
        opts.merge = 1;
        opts.clone = 1;
        opts.preserve_ignored = 0;
        opts.fn = oneway_merge;
        opts.verbose_update = (option_verbosity >= 0);
        opts.src_index = the_repository->index;
        opts.dst_index = the_repository->index;
        init_checkout_metadata(&opts.meta, head, &oid, NULL);

        tree = parse_tree_indirect(&oid);
        if (!tree)
                die(_("unable to parse commit %s"), oid_to_hex(&oid));
        if (parse_tree(tree) < 0)
                exit(128);
        init_tree_desc(&t, &tree->object.oid, tree->buffer, tree->size);
        if (unpack_trees(1, &t, &opts) < 0)
                die(_("unable to checkout working tree"));

        free(head);

        if (write_locked_index(the_repository->index, &lock_file, COMMIT_LOCK))
                die(_("unable to write new index file"));

        err |= run_hooks_l("post-checkout", oid_to_hex(null_oid()),
                           oid_to_hex(&oid), "1", NULL);

        if (!err && (option_recurse_submodules.nr > 0)) {
                struct child_process cmd = CHILD_PROCESS_INIT;
                strvec_pushl(&cmd.args, "submodule", "update", "--require-init",
                             "--recursive", NULL);

                if (option_shallow_submodules == 1)
                        strvec_push(&cmd.args, "--depth=1");

                if (max_jobs != -1)
                        strvec_pushf(&cmd.args, "--jobs=%d", max_jobs);

                if (submodule_progress)
                        strvec_push(&cmd.args, "--progress");

                if (option_verbosity < 0)
                        strvec_push(&cmd.args, "--quiet");

                if (option_remote_submodules) {
                        strvec_push(&cmd.args, "--remote");
                        strvec_push(&cmd.args, "--no-fetch");
                }

                if (filter_submodules && filter_options.choice)
                        strvec_pushf(&cmd.args, "--filter=%s",
                                     expand_list_objects_filter_spec(&filter_options));

                if (option_single_branch >= 0)
                        strvec_push(&cmd.args, option_single_branch ?
                                               "--single-branch" :
                                               "--no-single-branch");

                cmd.git_cmd = 1;
                err = run_command(&cmd);
        }

        return err;
}

static int git_clone_config(const char *k, const char *v,
                            const struct config_context *ctx, void *cb)
{
        if (!strcmp(k, "clone.defaultremotename")) {
                if (!v)
                        return config_error_nonbool(k);
                free(remote_name);
                remote_name = xstrdup(v);
        }
        if (!strcmp(k, "clone.rejectshallow"))
                config_reject_shallow = git_config_bool(k, v);
        if (!strcmp(k, "clone.filtersubmodules"))
                config_filter_submodules = git_config_bool(k, v);

        return git_default_config(k, v, ctx, cb);
}

static int write_one_config(const char *key, const char *value,
                            const struct config_context *ctx,
                            void *data)
{
        /*
         * give git_clone_config a chance to write config values back to the
         * environment, since git_config_set_multivar_gently only deals with
         * config-file writes
         */
        int apply_failed = git_clone_config(key, value, ctx, data);
        if (apply_failed)
                return apply_failed;

        return git_config_set_multivar_gently(key,
                                              value ? value : "true",
                                              CONFIG_REGEX_NONE, 0);
}

static void write_config(struct string_list *config)
{
        int i;

        for (i = 0; i < config->nr; i++) {
                if (git_config_parse_parameter(config->items[i].string,
                                               write_one_config, NULL) < 0)
                        die(_("unable to write parameters to config file"));
        }
}

static void write_refspec_config(const char *src_ref_prefix,
                const struct ref *our_head_points_at,
                const struct ref *remote_head_points_at,
                struct strbuf *branch_top)
{
        struct strbuf key = STRBUF_INIT;
        struct strbuf value = STRBUF_INIT;

        if (option_mirror || !option_bare) {
                if (option_single_branch && !option_mirror) {
                        if (option_branch) {
                                if (starts_with(our_head_points_at->name, "refs/tags/"))
                                        strbuf_addf(&value, "+%s:%s", our_head_points_at->name,
                                                our_head_points_at->name);
                                else
                                        strbuf_addf(&value, "+%s:%s%s", our_head_points_at->name,
                                                branch_top->buf, option_branch);
                        } else if (remote_head_points_at) {
                                const char *head = remote_head_points_at->name;
                                if (!skip_prefix(head, "refs/heads/", &head))
                                        BUG("remote HEAD points at non-head?");

                                strbuf_addf(&value, "+%s:%s%s", remote_head_points_at->name,
                                                branch_top->buf, head);
                        }
                        /*
                         * otherwise, the next "git fetch" will
                         * simply fetch from HEAD without updating
                         * any remote-tracking branch, which is what
                         * we want.
                         */
                } else {
                        strbuf_addf(&value, "+%s*:%s*", src_ref_prefix, branch_top->buf);
                }
                /* Configure the remote */
                if (value.len) {
                        strbuf_addf(&key, "remote.%s.fetch", remote_name);
                        git_config_set_multivar(key.buf, value.buf, "^$", 0);
                        strbuf_reset(&key);

                        if (option_mirror) {
                                strbuf_addf(&key, "remote.%s.mirror", remote_name);
                                git_config_set(key.buf, "true");
                                strbuf_reset(&key);
                        }
                }
        }

        strbuf_release(&key);
        strbuf_release(&value);
}

static void dissociate_from_references(void)
{
        char *alternates = git_pathdup("objects/info/alternates");

        if (!access(alternates, F_OK)) {
                struct child_process cmd = CHILD_PROCESS_INIT;

                cmd.git_cmd = 1;
                cmd.no_stdin = 1;
                strvec_pushl(&cmd.args, "repack", "-a", "-d", NULL);
                if (run_command(&cmd))
                        die(_("cannot repack to clean up"));
                if (unlink(alternates) && errno != ENOENT)
                        die_errno(_("cannot unlink temporary alternates file"));
        }
        free(alternates);
}

static int path_exists(const char *path)
{
        struct stat sb;
        return !stat(path, &sb);
}

int cmd_clone(int argc, const char **argv, const char *prefix)
{
        int is_bundle = 0, is_local;
        int reject_shallow = 0;
        const char *repo_name, *repo, *work_tree, *git_dir;
        char *repo_to_free = NULL;
        char *path = NULL, *dir, *display_repo = NULL;
        int dest_exists, real_dest_exists = 0;
        const struct ref *refs, *remote_head;
        struct ref *remote_head_points_at = NULL;
        const struct ref *our_head_points_at;
        char *unborn_head = NULL;
        struct ref *mapped_refs = NULL;
        const struct ref *ref;
        struct strbuf key = STRBUF_INIT;
        struct strbuf buf = STRBUF_INIT;
        struct strbuf branch_top = STRBUF_INIT, reflog_msg = STRBUF_INIT;
        struct transport *transport = NULL;
        const char *src_ref_prefix = "refs/heads/";
        struct remote *remote;
        int err = 0, complete_refs_before_fetch = 1;
        int submodule_progress;
        int filter_submodules = 0;
        int hash_algo;
        unsigned int ref_storage_format = REF_STORAGE_FORMAT_UNKNOWN;
        const int do_not_override_repo_unix_permissions = -1;
        const char *template_dir;
        char *template_dir_dup = NULL;

        struct transport_ls_refs_options transport_ls_refs_options =
                TRANSPORT_LS_REFS_OPTIONS_INIT;

        packet_trace_identity("clone");

        git_config(git_clone_config, NULL);

        argc = parse_options(argc, argv, prefix, builtin_clone_options,
                             builtin_clone_usage, 0);

        if (argc > 2)
                usage_msg_opt(_("Too many arguments."),
                        builtin_clone_usage, builtin_clone_options);

        if (argc == 0)
                usage_msg_opt(_("You must specify a repository to clone."),
                        builtin_clone_usage, builtin_clone_options);

        xsetenv("GIT_CLONE_PROTECTION_ACTIVE", "true", 0 /* allow user override */);
        template_dir = get_template_dir(option_template);
        if (*template_dir && !is_absolute_path(template_dir))
                template_dir = template_dir_dup =
                        absolute_pathdup(template_dir);
        xsetenv("GIT_CLONE_TEMPLATE_DIR", template_dir, 1);

        if (option_depth || option_since || option_not.nr)
                deepen = 1;
        if (option_single_branch == -1)
                option_single_branch = deepen ? 1 : 0;

        if (ref_format) {
                ref_storage_format = ref_storage_format_by_name(ref_format);
                if (ref_storage_format == REF_STORAGE_FORMAT_UNKNOWN)
                        die(_("unknown ref storage format '%s'"), ref_format);
        }

        if (option_mirror)
                option_bare = 1;

        if (option_bare) {
                if (real_git_dir)
                        die(_("options '%s' and '%s' cannot be used together"), "--bare", "--separate-git-dir");
                option_no_checkout = 1;
        }

        if (bundle_uri && deepen)
                die(_("options '%s' and '%s' cannot be used together"),
                    "--bundle-uri",
                    "--depth/--shallow-since/--shallow-exclude");

        repo_name = argv[0];

        path = get_repo_path(repo_name, &is_bundle);
        if (path) {
                FREE_AND_NULL(path);
                repo = repo_to_free = absolute_pathdup(repo_name);
        } else if (strchr(repo_name, ':')) {
                repo = repo_name;
                display_repo = transport_anonymize_url(repo);
        } else
                die(_("repository '%s' does not exist"), repo_name);

        /* no need to be strict, transport_set_option() will validate it again */
        if (option_depth && atoi(option_depth) < 1)
                die(_("depth %s is not a positive number"), option_depth);

        if (argc == 2)
                dir = xstrdup(argv[1]);
        else
                dir = git_url_basename(repo_name, is_bundle, option_bare);
        strip_dir_trailing_slashes(dir);

        dest_exists = path_exists(dir);
        if (dest_exists && !is_empty_dir(dir))
                die(_("destination path '%s' already exists and is not "
                        "an empty directory."), dir);

        if (real_git_dir) {
                real_dest_exists = path_exists(real_git_dir);
                if (real_dest_exists && !is_empty_dir(real_git_dir))
                        die(_("repository path '%s' already exists and is not "
                                "an empty directory."), real_git_dir);
        }


        strbuf_addf(&reflog_msg, "clone: from %s",
                    display_repo ? display_repo : repo);
        free(display_repo);

        if (option_bare)
                work_tree = NULL;
        else {
                work_tree = getenv("GIT_WORK_TREE");
                if (work_tree && path_exists(work_tree))
                        die(_("working tree '%s' already exists."), work_tree);
        }

        if (option_bare || work_tree)
                git_dir = xstrdup(dir);
        else {
                work_tree = dir;
                git_dir = mkpathdup("%s/.git", dir);
        }

        atexit(remove_junk);
        sigchain_push_common(remove_junk_on_signal);

        if (!option_bare) {
                if (safe_create_leading_directories_const(work_tree) < 0)
                        die_errno(_("could not create leading directories of '%s'"),
                                  work_tree);
                if (dest_exists)
                        junk_work_tree_flags |= REMOVE_DIR_KEEP_TOPLEVEL;
                else if (mkdir(work_tree, 0777))
                        die_errno(_("could not create work tree dir '%s'"),
                                  work_tree);
                junk_work_tree = work_tree;
                set_git_work_tree(work_tree);
        }

        if (real_git_dir) {
                if (real_dest_exists)
                        junk_git_dir_flags |= REMOVE_DIR_KEEP_TOPLEVEL;
                junk_git_dir = real_git_dir;
        } else {
                if (dest_exists)
                        junk_git_dir_flags |= REMOVE_DIR_KEEP_TOPLEVEL;
                junk_git_dir = git_dir;
        }
        if (safe_create_leading_directories_const(git_dir) < 0)
                die(_("could not create leading directories of '%s'"), git_dir);

        if (0 <= option_verbosity) {
                if (option_bare)
                        fprintf(stderr, _("Cloning into bare repository '%s'...\n"), dir);
                else
                        fprintf(stderr, _("Cloning into '%s'...\n"), dir);
        }

        if (option_recurse_submodules.nr > 0) {
                struct string_list_item *item;
                struct strbuf sb = STRBUF_INIT;
                int val;

                /* remove duplicates */
                string_list_sort(&option_recurse_submodules);
                string_list_remove_duplicates(&option_recurse_submodules, 0);

                /*
                 * NEEDSWORK: In a multi-working-tree world, this needs to be
                 * set in the per-worktree config.
                 */
                for_each_string_list_item(item, &option_recurse_submodules) {
                        strbuf_addf(&sb, "submodule.active=%s",
                                    item->string);
                        string_list_append(&option_config,
                                           strbuf_detach(&sb, NULL));
                }

                if (!git_config_get_bool("submodule.stickyRecursiveClone", &val) &&
                    val)
                        string_list_append(&option_config, "submodule.recurse=true");

                if (option_required_reference.nr &&
                    option_optional_reference.nr)
                        die(_("clone --recursive is not compatible with "
                              "both --reference and --reference-if-able"));
                else if (option_required_reference.nr) {
                        string_list_append(&option_config,
                                "submodule.alternateLocation=superproject");
                        string_list_append(&option_config,
                                "submodule.alternateErrorStrategy=die");
                } else if (option_optional_reference.nr) {
                        string_list_append(&option_config,
                                "submodule.alternateLocation=superproject");
                        string_list_append(&option_config,
                                "submodule.alternateErrorStrategy=info");
                }
        }

        /*
         * Initialize the repository, but skip initializing the reference
         * database. We do not yet know about the object format of the
         * repository, and reference backends may persist that information into
         * their on-disk data structures.
         */
        init_db(git_dir, real_git_dir, template_dir, GIT_HASH_UNKNOWN,
                ref_storage_format, NULL,
                do_not_override_repo_unix_permissions, INIT_DB_QUIET | INIT_DB_SKIP_REFDB);

        if (real_git_dir) {
                free((char *)git_dir);
                git_dir = real_git_dir;
        }

        /*
         * We have a chicken-and-egg situation between initializing the refdb
         * and spawning transport helpers:
         *
         *   - Initializing the refdb requires us to know about the object
         *     format. We thus have to spawn the transport helper to learn
         *     about it.
         *
         *   - The transport helper may want to access the Git repository. But
         *     because the refdb has not been initialized, we don't have "HEAD"
         *     or "refs/". Thus, the helper cannot find the Git repository.
         *
         * Ideally, we would have structured the helper protocol such that it's
         * mandatory for the helper to first announce its capabilities without
         * yet assuming a fully initialized repository. Like that, we could
         * have added a "lazy-refdb-init" capability that announces whether the
         * helper is ready to handle not-yet-initialized refdbs. If any helper
         * didn't support them, we would have fully initialized the refdb with
         * the SHA1 object format, but later on bailed out if we found out that
         * the remote repository used a different object format.
         *
         * But we didn't, and thus we use the following workaround to partially
         * initialize the repository's refdb such that it can be discovered by
         * Git commands. To do so, we:
         *
         *   - Create an invalid HEAD ref pointing at "refs/heads/.invalid".
         *
         *   - Create the "refs/" directory.
         *
         *   - Set up the ref storage format and repository version as
         *     required.
         *
         * This is sufficient for Git commands to discover the Git directory.
         */
        initialize_repository_version(GIT_HASH_UNKNOWN,
                                      the_repository->ref_storage_format, 1);

        strbuf_addf(&buf, "%s/HEAD", git_dir);
        write_file(buf.buf, "ref: refs/heads/.invalid");

        strbuf_reset(&buf);
        strbuf_addf(&buf, "%s/refs", git_dir);
        safe_create_dir(buf.buf, 1);

        /*
         * additional config can be injected with -c, make sure it's included
         * after init_db, which clears the entire config environment.
         */
        write_config(&option_config);

        /*
         * re-read config after init_db and write_config to pick up any config
         * injected by --template and --config, respectively.
         */
        git_config(git_clone_config, NULL);

        /*
         * If option_reject_shallow is specified from CLI option,
         * ignore config_reject_shallow from git_clone_config.
         */
        if (config_reject_shallow != -1)
                reject_shallow = config_reject_shallow;
        if (option_reject_shallow != -1)
                reject_shallow = option_reject_shallow;

        /*
         * If option_filter_submodules is specified from CLI option,
         * ignore config_filter_submodules from git_clone_config.
         */
        if (config_filter_submodules != -1)
                filter_submodules = config_filter_submodules;
        if (option_filter_submodules != -1)
                filter_submodules = option_filter_submodules;

        /*
         * Exit if the user seems to be doing something silly with submodule
         * filter flags (but not with filter configs, as those should be
         * set-and-forget).
         */
        if (option_filter_submodules > 0 && !filter_options.choice)
                die(_("the option '%s' requires '%s'"),
                    "--also-filter-submodules", "--filter");
        if (option_filter_submodules > 0 && !option_recurse_submodules.nr)
                die(_("the option '%s' requires '%s'"),
                    "--also-filter-submodules", "--recurse-submodules");

        /*
         * apply the remote name provided by --origin only after this second
         * call to git_config, to ensure it overrides all config-based values.
         */
        if (option_origin) {
                free(remote_name);
                remote_name = xstrdup(option_origin);
        }

        if (!remote_name)
                remote_name = xstrdup("origin");

        if (!valid_remote_name(remote_name))
                die(_("'%s' is not a valid remote name"), remote_name);

        if (option_bare) {
                if (option_mirror)
                        src_ref_prefix = "refs/";
                strbuf_addstr(&branch_top, src_ref_prefix);

                git_config_set("core.bare", "true");
        } else {
                strbuf_addf(&branch_top, "refs/remotes/%s/", remote_name);
        }

        strbuf_addf(&key, "remote.%s.url", remote_name);
        git_config_set(key.buf, repo);
        strbuf_reset(&key);

        if (option_no_tags) {
                strbuf_addf(&key, "remote.%s.tagOpt", remote_name);
                git_config_set(key.buf, "--no-tags");
                strbuf_reset(&key);
        }

        if (option_required_reference.nr || option_optional_reference.nr)
                setup_reference();

        remote = remote_get_early(remote_name);

        refspec_appendf(&remote->fetch, "+%s*:%s*", src_ref_prefix,
                        branch_top.buf);

        path = get_repo_path(remote->url[0], &is_bundle);
        is_local = option_local != 0 && path && !is_bundle;
        if (is_local) {
                if (option_depth)
                        warning(_("--depth is ignored in local clones; use file:// instead."));
                if (option_since)
                        warning(_("--shallow-since is ignored in local clones; use file:// instead."));
                if (option_not.nr)
                        warning(_("--shallow-exclude is ignored in local clones; use file:// instead."));
                if (filter_options.choice)
                        warning(_("--filter is ignored in local clones; use file:// instead."));
                if (!access(mkpath("%s/shallow", path), F_OK)) {
                        if (reject_shallow)
                                die(_("source repository is shallow, reject to clone."));
                        if (option_local > 0)
                                warning(_("source repository is shallow, ignoring --local"));
                        is_local = 0;
                }
        }
        if (option_local > 0 && !is_local)
                warning(_("--local is ignored"));

        transport = transport_get(remote, path ? path : remote->url[0]);
        transport_set_verbosity(transport, option_verbosity, option_progress);
        transport->family = family;
        transport->cloning = 1;

        if (is_bundle) {
                struct bundle_header header = BUNDLE_HEADER_INIT;
                int fd = read_bundle_header(path, &header);
                int has_filter = header.filter.choice != LOFC_DISABLED;

                if (fd > 0)
                        close(fd);
                bundle_header_release(&header);
                if (has_filter)
                        die(_("cannot clone from filtered bundle"));
        }

        transport_set_option(transport, TRANS_OPT_KEEP, "yes");

        if (reject_shallow)
                transport_set_option(transport, TRANS_OPT_REJECT_SHALLOW, "1");
        if (option_depth)
                transport_set_option(transport, TRANS_OPT_DEPTH,
                                     option_depth);
        if (option_since)
                transport_set_option(transport, TRANS_OPT_DEEPEN_SINCE,
                                     option_since);
        if (option_not.nr)
                transport_set_option(transport, TRANS_OPT_DEEPEN_NOT,
                                     (const char *)&option_not);
        if (option_single_branch)
                transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, "1");

        if (option_upload_pack)
                transport_set_option(transport, TRANS_OPT_UPLOADPACK,
                                     option_upload_pack);

        if (server_options.nr)
                transport->server_options = &server_options;

        if (filter_options.choice) {
                const char *spec =
                        expand_list_objects_filter_spec(&filter_options);
                transport_set_option(transport, TRANS_OPT_LIST_OBJECTS_FILTER,
                                     spec);
                transport_set_option(transport, TRANS_OPT_FROM_PROMISOR, "1");
        }

        if (transport->smart_options && !deepen && !filter_options.choice)
                transport->smart_options->check_self_contained_and_connected = 1;

        strvec_push(&transport_ls_refs_options.ref_prefixes, "HEAD");
        refspec_ref_prefixes(&remote->fetch,
                             &transport_ls_refs_options.ref_prefixes);
        if (option_branch)
                expand_ref_prefix(&transport_ls_refs_options.ref_prefixes,
                                  option_branch);
        if (!option_no_tags)
                strvec_push(&transport_ls_refs_options.ref_prefixes,
                            "refs/tags/");

        refs = transport_get_remote_refs(transport, &transport_ls_refs_options);

        /*
         * Now that we know what algorithm the remote side is using, let's set
         * ours to the same thing.
         */
        hash_algo = hash_algo_by_ptr(transport_get_hash_algo(transport));
        initialize_repository_version(hash_algo, the_repository->ref_storage_format, 1);
        repo_set_hash_algo(the_repository, hash_algo);
        create_reference_database(the_repository->ref_storage_format, NULL, 1);

        /*
         * Before fetching from the remote, download and install bundle
         * data from the --bundle-uri option.
         */
        if (bundle_uri) {
                int has_heuristic = 0;

                /* At this point, we need the_repository to match the cloned repo. */
                if (repo_init(the_repository, git_dir, work_tree))
                        warning(_("failed to initialize the repo, skipping bundle URI"));
                else if (fetch_bundle_uri(the_repository, bundle_uri, &has_heuristic))
                        warning(_("failed to fetch objects from bundle URI '%s'"),
                                bundle_uri);
                else if (has_heuristic)
                        git_config_set_gently("fetch.bundleuri", bundle_uri);
        } else {
                /*
                * Populate transport->got_remote_bundle_uri and
                * transport->bundle_uri. We might get nothing.
                */
                transport_get_remote_bundle_uri(transport);

                if (transport->bundles &&
                    hashmap_get_size(&transport->bundles->bundles)) {
                        /* At this point, we need the_repository to match the cloned repo. */
                        if (repo_init(the_repository, git_dir, work_tree))
                                warning(_("failed to initialize the repo, skipping bundle URI"));
                        else if (fetch_bundle_list(the_repository,
                                                   transport->bundles))
                                warning(_("failed to fetch advertised bundles"));
                } else {
                        clear_bundle_list(transport->bundles);
                        FREE_AND_NULL(transport->bundles);
                }
        }

        if (refs)
                mapped_refs = wanted_peer_refs(refs, &remote->fetch);

        if (mapped_refs) {
                /*
                 * transport_get_remote_refs() may return refs with null sha-1
                 * in mapped_refs (see struct transport->get_refs_list
                 * comment). In that case we need fetch it early because
                 * remote_head code below relies on it.
                 *
                 * for normal clones, transport_get_remote_refs() should
                 * return reliable ref set, we can delay cloning until after
                 * remote HEAD check.
                 */
                for (ref = refs; ref; ref = ref->next)
                        if (is_null_oid(&ref->old_oid)) {
                                complete_refs_before_fetch = 0;
                                break;
                        }

                if (!is_local && !complete_refs_before_fetch) {
                        if (transport_fetch_refs(transport, mapped_refs))
                                die(_("remote transport reported error"));
                }
        }

        remote_head = find_ref_by_name(refs, "HEAD");
        remote_head_points_at = guess_remote_head(remote_head, mapped_refs, 0);

        if (option_branch) {
                our_head_points_at = find_remote_branch(mapped_refs, option_branch);
                if (!our_head_points_at)
                        die(_("Remote branch %s not found in upstream %s"),
                            option_branch, remote_name);
        } else if (remote_head_points_at) {
                our_head_points_at = remote_head_points_at;
        } else if (remote_head) {
                our_head_points_at = NULL;
        } else {
                const char *branch;

                if (!mapped_refs) {
                        warning(_("You appear to have cloned an empty repository."));
                        option_no_checkout = 1;
                }

                if (transport_ls_refs_options.unborn_head_target &&
                    skip_prefix(transport_ls_refs_options.unborn_head_target,
                                "refs/heads/", &branch)) {
                        unborn_head  = xstrdup(transport_ls_refs_options.unborn_head_target);
                } else {
                        branch = git_default_branch_name(0);
                        unborn_head = xstrfmt("refs/heads/%s", branch);
                }

                /*
                 * We may have selected a local default branch name "foo",
                 * and even though the remote's HEAD does not point there,
                 * it may still have a "foo" branch. If so, set it up so
                 * that we can follow the usual checkout code later.
                 *
                 * Note that for an empty repo we'll already have set
                 * option_no_checkout above, which would work against us here.
                 * But for an empty repo, find_remote_branch() can never find
                 * a match.
                 */
                our_head_points_at = find_remote_branch(mapped_refs, branch);
        }

        write_refspec_config(src_ref_prefix, our_head_points_at,
                        remote_head_points_at, &branch_top);

        if (filter_options.choice)
                partial_clone_register(remote_name, &filter_options);

        if (is_local)
                clone_local(path, git_dir);
        else if (mapped_refs && complete_refs_before_fetch) {
                if (transport_fetch_refs(transport, mapped_refs))
                        die(_("remote transport reported error"));
        }

        update_remote_refs(refs, mapped_refs, remote_head_points_at,
                           branch_top.buf, reflog_msg.buf, transport,
                           !is_local);

        update_head(our_head_points_at, remote_head, unborn_head, reflog_msg.buf);

        /*
         * We want to show progress for recursive submodule clones iff
         * we did so for the main clone. But only the transport knows
         * the final decision for this flag, so we need to rescue the value
         * before we free the transport.
         */
        submodule_progress = transport->progress;

        transport_unlock_pack(transport, 0);
        transport_disconnect(transport);

        if (option_dissociate) {
                close_object_store(the_repository->objects);
                dissociate_from_references();
        }

        if (option_sparse_checkout && git_sparse_checkout_init(dir))
                return 1;

        junk_mode = JUNK_LEAVE_REPO;
        err = checkout(submodule_progress, filter_submodules);

        free(remote_name);
        strbuf_release(&reflog_msg);
        strbuf_release(&branch_top);
        strbuf_release(&buf);
        strbuf_release(&key);
        free_refs(mapped_refs);
        free_refs(remote_head_points_at);
        free(unborn_head);
        free(dir);
        free(path);
        free(repo_to_free);
        free(template_dir_dup);
        junk_mode = JUNK_LEAVE_ALL;

        transport_ls_refs_options_release(&transport_ls_refs_options);
        return err;
}