get_sha1(): fix error status regression
[gitweb.git] / transport-helper.c
index f822972020136b0fa04a95d7fcf26df40c81cfe6..6f227e253bf638de37ce74347213657c23185afa 100644 (file)
@@ -7,20 +7,24 @@
 #include "revision.h"
 #include "quote.h"
 #include "remote.h"
+#include "string-list.h"
+#include "thread-utils.h"
 
 static int debug;
 
-struct helper_data
-{
+struct helper_data {
        const char *name;
        struct child_process *helper;
        FILE *out;
        unsigned fetch : 1,
                import : 1,
+               export : 1,
                option : 1,
                push : 1,
                connect : 1,
                no_disconnect_req : 1;
+       char *export_marks;
+       char *import_marks;
        /* These go from remote name (as in "list") to private name */
        struct refspec *refspecs;
        int refspec_nr;
@@ -74,7 +78,7 @@ static void write_constant(int fd, const char *str)
                die_errno("Full write to remote helper failed");
 }
 
-const char *remove_ext_force(const char *url)
+static const char *remove_ext_force(const char *url)
 {
        if (url) {
                const char *colon = strchr(url, ':');
@@ -103,6 +107,12 @@ static struct child_process *get_helper(struct transport *transport)
        int refspec_alloc = 0;
        int duped;
        int code;
+       char git_dir_buf[sizeof(GIT_DIR_ENVIRONMENT) + PATH_MAX + 1];
+       const char *helper_env[] = {
+               git_dir_buf,
+               NULL
+       };
+
 
        if (data->helper)
                return data->helper;
@@ -118,6 +128,10 @@ static struct child_process *get_helper(struct transport *transport)
        helper->argv[2] = remove_ext_force(transport->url);
        helper->git_cmd = 0;
        helper->silent_exec_failure = 1;
+
+       snprintf(git_dir_buf, sizeof(git_dir_buf), "%s=%s", GIT_DIR_ENVIRONMENT, get_git_dir());
+       helper->env = helper_env;
+
        code = start_command(helper);
        if (code < 0 && errno == ENOENT)
                die("Unable to find remote helper for '%s'", data->name);
@@ -163,13 +177,25 @@ static struct child_process *get_helper(struct transport *transport)
                        data->push = 1;
                else if (!strcmp(capname, "import"))
                        data->import = 1;
+               else if (!strcmp(capname, "export"))
+                       data->export = 1;
                else if (!data->refspecs && !prefixcmp(capname, "refspec ")) {
                        ALLOC_GROW(refspecs,
                                   refspec_nr + 1,
                                   refspec_alloc);
-                       refspecs[refspec_nr++] = strdup(buf.buf + strlen("refspec "));
+                       refspecs[refspec_nr++] = xstrdup(capname + strlen("refspec "));
                } else if (!strcmp(capname, "connect")) {
                        data->connect = 1;
+               } else if (!prefixcmp(capname, "export-marks ")) {
+                       struct strbuf arg = STRBUF_INIT;
+                       strbuf_addstr(&arg, "--export-marks=");
+                       strbuf_addstr(&arg, capname + strlen("export-marks "));
+                       data->export_marks = strbuf_detach(&arg, NULL);
+               } else if (!prefixcmp(capname, "import-marks")) {
+                       struct strbuf arg = STRBUF_INIT;
+                       strbuf_addstr(&arg, "--import-marks=");
+                       strbuf_addstr(&arg, capname + strlen("import-marks "));
+                       data->import_marks = strbuf_detach(&arg, NULL);
                } else if (mandatory) {
                        die("Unknown mandatory capability %s. This remote "
                            "helper probably needs newer version of Git.\n",
@@ -195,6 +221,7 @@ static int disconnect_helper(struct transport *transport)
 {
        struct helper_data *data = transport->data;
        struct strbuf buf = STRBUF_INIT;
+       int res = 0;
 
        if (data->helper) {
                if (debug)
@@ -206,13 +233,13 @@ static int disconnect_helper(struct transport *transport)
                close(data->helper->in);
                close(data->helper->out);
                fclose(data->out);
-               finish_command(data->helper);
+               res = finish_command(data->helper);
                free((char *)data->helper->argv[0]);
                free(data->helper->argv);
                free(data->helper);
                data->helper = NULL;
        }
-       return 0;
+       return res;
 }
 
 static const char *unsupported_options[] = {
@@ -279,9 +306,8 @@ static void standard_options(struct transport *t)
        char buf[16];
        int n;
        int v = t->verbose;
-       int no_progress = v < 0 || (!t->progress && !isatty(2));
 
-       set_helper_option(t, "progress", !no_progress ? "true" : "false");
+       set_helper_option(t, "progress", t->progress ? "true" : "false");
 
        n = snprintf(buf, sizeof(buf), "%d", v + 1);
        if (n >= sizeof(buf))
@@ -291,12 +317,13 @@ static void standard_options(struct transport *t)
 
 static int release_helper(struct transport *transport)
 {
+       int res = 0;
        struct helper_data *data = transport->data;
        free_refspec(data->refspec_nr, data->refspecs);
        data->refspecs = NULL;
-       disconnect_helper(transport);
+       res = disconnect_helper(transport);
        free(transport->data);
-       return 0;
+       return res;
 }
 
 static int fetch_with_fetch(struct transport *transport,
@@ -352,6 +379,33 @@ static int get_importer(struct transport *transport, struct child_process *fasti
        return start_command(fastimport);
 }
 
+static int get_exporter(struct transport *transport,
+                       struct child_process *fastexport,
+                       struct string_list *revlist_args)
+{
+       struct helper_data *data = transport->data;
+       struct child_process *helper = get_helper(transport);
+       int argc = 0, i;
+       memset(fastexport, 0, sizeof(*fastexport));
+
+       /* we need to duplicate helper->in because we want to use it after
+        * fastexport is done with it. */
+       fastexport->out = dup(helper->in);
+       fastexport->argv = xcalloc(5 + revlist_args->nr, sizeof(*fastexport->argv));
+       fastexport->argv[argc++] = "fast-export";
+       fastexport->argv[argc++] = "--use-done-feature";
+       if (data->export_marks)
+               fastexport->argv[argc++] = data->export_marks;
+       if (data->import_marks)
+               fastexport->argv[argc++] = data->import_marks;
+
+       for (i = 0; i < revlist_args->nr; i++)
+               fastexport->argv[argc++] = revlist_args->items[i].string;
+
+       fastexport->git_cmd = 1;
+       return start_command(fastexport);
+}
+
 static int fetch_with_import(struct transport *transport,
                             int nr_heads, struct ref **to_fetch)
 {
@@ -375,8 +429,11 @@ static int fetch_with_import(struct transport *transport,
                sendline(data, &buf);
                strbuf_reset(&buf);
        }
-       disconnect_helper(transport);
-       finish_command(&fastimport);
+
+       write_constant(data->helper->in, "\n");
+
+       if (finish_command(&fastimport))
+               die("Error while running fast-import");
        free(fastimport.argv);
        fastimport.argv = NULL;
 
@@ -388,9 +445,11 @@ static int fetch_with_import(struct transport *transport,
                if (data->refspecs)
                        private = apply_refspecs(data->refspecs, data->refspec_nr, posn->name);
                else
-                       private = strdup(posn->name);
-               read_ref(private, posn->old_sha1);
-               free(private);
+                       private = xstrdup(posn->name);
+               if (private) {
+                       read_ref(private, posn->old_sha1);
+                       free(private);
+               }
        }
        strbuf_release(&buf);
        return 0;
@@ -519,28 +578,98 @@ static int fetch(struct transport *transport,
        return -1;
 }
 
-static int push_refs(struct transport *transport,
+static void push_update_ref_status(struct strbuf *buf,
+                                  struct ref **ref,
+                                  struct ref *remote_refs)
+{
+       char *refname, *msg;
+       int status;
+
+       if (!prefixcmp(buf->buf, "ok ")) {
+               status = REF_STATUS_OK;
+               refname = buf->buf + 3;
+       } else if (!prefixcmp(buf->buf, "error ")) {
+               status = REF_STATUS_REMOTE_REJECT;
+               refname = buf->buf + 6;
+       } else
+               die("expected ok/error, helper said '%s'\n", buf->buf);
+
+       msg = strchr(refname, ' ');
+       if (msg) {
+               struct strbuf msg_buf = STRBUF_INIT;
+               const char *end;
+
+               *msg++ = '\0';
+               if (!unquote_c_style(&msg_buf, msg, &end))
+                       msg = strbuf_detach(&msg_buf, NULL);
+               else
+                       msg = xstrdup(msg);
+               strbuf_release(&msg_buf);
+
+               if (!strcmp(msg, "no match")) {
+                       status = REF_STATUS_NONE;
+                       free(msg);
+                       msg = NULL;
+               }
+               else if (!strcmp(msg, "up to date")) {
+                       status = REF_STATUS_UPTODATE;
+                       free(msg);
+                       msg = NULL;
+               }
+               else if (!strcmp(msg, "non-fast forward")) {
+                       status = REF_STATUS_REJECT_NONFASTFORWARD;
+                       free(msg);
+                       msg = NULL;
+               }
+       }
+
+       if (*ref)
+               *ref = find_ref_by_name(*ref, refname);
+       if (!*ref)
+               *ref = find_ref_by_name(remote_refs, refname);
+       if (!*ref) {
+               warning("helper reported unexpected status of %s", refname);
+               return;
+       }
+
+       if ((*ref)->status != REF_STATUS_NONE) {
+               /*
+                * Earlier, the ref was marked not to be pushed, so ignore the ref
+                * status reported by the remote helper if the latter is 'no match'.
+                */
+               if (status == REF_STATUS_NONE)
+                       return;
+       }
+
+       (*ref)->status = status;
+       (*ref)->remote_status = msg;
+}
+
+static void push_update_refs_status(struct helper_data *data,
+                                   struct ref *remote_refs)
+{
+       struct strbuf buf = STRBUF_INIT;
+       struct ref *ref = remote_refs;
+       for (;;) {
+               recvline(data, &buf);
+               if (!buf.len)
+                       break;
+
+               push_update_ref_status(&buf, &ref, remote_refs);
+       }
+       strbuf_release(&buf);
+}
+
+static int push_refs_with_push(struct transport *transport,
                struct ref *remote_refs, int flags)
 {
        int force_all = flags & TRANSPORT_PUSH_FORCE;
        int mirror = flags & TRANSPORT_PUSH_MIRROR;
        struct helper_data *data = transport->data;
        struct strbuf buf = STRBUF_INIT;
-       struct child_process *helper;
        struct ref *ref;
 
-       if (process_connect(transport, 1)) {
-               do_take_over(transport);
-               return transport->push_refs(transport, remote_refs, flags);
-       }
-
-       if (!remote_refs) {
-               fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
-                       "Perhaps you should specify a branch such as 'master'.\n");
-               return 0;
-       }
-
-       helper = get_helper(transport);
+       get_helper(transport);
        if (!data->push)
                return 1;
 
@@ -576,7 +705,6 @@ static int push_refs(struct transport *transport,
        if (buf.len == 0)
                return 0;
 
-       transport->verbose = flags & TRANSPORT_PUSH_VERBOSE ? 1 : 0;
        standard_options(transport);
 
        if (flags & TRANSPORT_PUSH_DRY_RUN) {
@@ -586,79 +714,84 @@ static int push_refs(struct transport *transport,
 
        strbuf_addch(&buf, '\n');
        sendline(data, &buf);
+       strbuf_release(&buf);
 
-       ref = remote_refs;
-       while (1) {
-               char *refname, *msg;
-               int status;
+       push_update_refs_status(data, remote_refs);
+       return 0;
+}
 
-               recvline(data, &buf);
-               if (!buf.len)
-                       break;
+static int push_refs_with_export(struct transport *transport,
+               struct ref *remote_refs, int flags)
+{
+       struct ref *ref;
+       struct child_process *helper, exporter;
+       struct helper_data *data = transport->data;
+       struct string_list revlist_args = STRING_LIST_INIT_NODUP;
+       struct strbuf buf = STRBUF_INIT;
 
-               if (!prefixcmp(buf.buf, "ok ")) {
-                       status = REF_STATUS_OK;
-                       refname = buf.buf + 3;
-               } else if (!prefixcmp(buf.buf, "error ")) {
-                       status = REF_STATUS_REMOTE_REJECT;
-                       refname = buf.buf + 6;
-               } else
-                       die("expected ok/error, helper said '%s'\n", buf.buf);
+       helper = get_helper(transport);
 
-               msg = strchr(refname, ' ');
-               if (msg) {
-                       struct strbuf msg_buf = STRBUF_INIT;
-                       const char *end;
+       write_constant(helper->in, "export\n");
 
-                       *msg++ = '\0';
-                       if (!unquote_c_style(&msg_buf, msg, &end))
-                               msg = strbuf_detach(&msg_buf, NULL);
-                       else
-                               msg = xstrdup(msg);
-                       strbuf_release(&msg_buf);
+       strbuf_reset(&buf);
 
-                       if (!strcmp(msg, "no match")) {
-                               status = REF_STATUS_NONE;
-                               free(msg);
-                               msg = NULL;
-                       }
-                       else if (!strcmp(msg, "up to date")) {
-                               status = REF_STATUS_UPTODATE;
-                               free(msg);
-                               msg = NULL;
-                       }
-                       else if (!strcmp(msg, "non-fast forward")) {
-                               status = REF_STATUS_REJECT_NONFASTFORWARD;
-                               free(msg);
-                               msg = NULL;
-                       }
-               }
+       for (ref = remote_refs; ref; ref = ref->next) {
+               char *private;
+               unsigned char sha1[20];
 
-               if (ref)
-                       ref = find_ref_by_name(ref, refname);
-               if (!ref)
-                       ref = find_ref_by_name(remote_refs, refname);
-               if (!ref) {
-                       warning("helper reported unexpected status of %s", refname);
+               if (!data->refspecs)
                        continue;
+               private = apply_refspecs(data->refspecs, data->refspec_nr, ref->name);
+               if (private && !get_sha1(private, sha1)) {
+                       strbuf_addf(&buf, "^%s", private);
+                       string_list_append(&revlist_args, strbuf_detach(&buf, NULL));
                }
+               free(private);
 
-               if (ref->status != REF_STATUS_NONE) {
-                       /*
-                        * Earlier, the ref was marked not to be pushed, so ignore the ref
-                        * status reported by the remote helper if the latter is 'no match'.
-                        */
-                       if (status == REF_STATUS_NONE)
-                               continue;
+               if (ref->deletion) {
+                       die("remote-helpers do not support ref deletion");
                }
 
-               ref->status = status;
-               ref->remote_status = msg;
+               if (ref->peer_ref)
+                       string_list_append(&revlist_args, ref->peer_ref->name);
+
        }
-       strbuf_release(&buf);
+
+       if (get_exporter(transport, &exporter, &revlist_args))
+               die("Couldn't run fast-export");
+
+       if (finish_command(&exporter))
+               die("Error while running fast-export");
+       push_update_refs_status(data, remote_refs);
        return 0;
 }
 
+static int push_refs(struct transport *transport,
+               struct ref *remote_refs, int flags)
+{
+       struct helper_data *data = transport->data;
+
+       if (process_connect(transport, 1)) {
+               do_take_over(transport);
+               return transport->push_refs(transport, remote_refs, flags);
+       }
+
+       if (!remote_refs) {
+               fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
+                       "Perhaps you should specify a branch such as 'master'.\n");
+               return 0;
+       }
+
+       if (data->push)
+               return push_refs_with_push(transport, remote_refs, flags);
+
+       if (data->export)
+               return push_refs_with_export(transport, remote_refs, flags);
+
+       return -1;
+}
+
+
 static int has_attribute(const char *attrs, const char *attr) {
        int len;
        if (!attrs)
@@ -751,3 +884,314 @@ int transport_helper_init(struct transport *transport, const char *name)
        transport->smart_options = &(data->transport_options);
        return 0;
 }
+
+/*
+ * Linux pipes can buffer 65536 bytes at once (and most platforms can
+ * buffer less), so attempt reads and writes with up to that size.
+ */
+#define BUFFERSIZE 65536
+/* This should be enough to hold debugging message. */
+#define PBUFFERSIZE 8192
+
+/* Print bidirectional transfer loop debug message. */
+static void transfer_debug(const char *fmt, ...)
+{
+       va_list args;
+       char msgbuf[PBUFFERSIZE];
+       static int debug_enabled = -1;
+
+       if (debug_enabled < 0)
+               debug_enabled = getenv("GIT_TRANSLOOP_DEBUG") ? 1 : 0;
+       if (!debug_enabled)
+               return;
+
+       va_start(args, fmt);
+       vsnprintf(msgbuf, PBUFFERSIZE, fmt, args);
+       va_end(args);
+       fprintf(stderr, "Transfer loop debugging: %s\n", msgbuf);
+}
+
+/* Stream state: More data may be coming in this direction. */
+#define SSTATE_TRANSFERING 0
+/*
+ * Stream state: No more data coming in this direction, flushing rest of
+ * data.
+ */
+#define SSTATE_FLUSHING 1
+/* Stream state: Transfer in this direction finished. */
+#define SSTATE_FINISHED 2
+
+#define STATE_NEEDS_READING(state) ((state) <= SSTATE_TRANSFERING)
+#define STATE_NEEDS_WRITING(state) ((state) <= SSTATE_FLUSHING)
+#define STATE_NEEDS_CLOSING(state) ((state) == SSTATE_FLUSHING)
+
+/* Unidirectional transfer. */
+struct unidirectional_transfer {
+       /* Source */
+       int src;
+       /* Destination */
+       int dest;
+       /* Is source socket? */
+       int src_is_sock;
+       /* Is destination socket? */
+       int dest_is_sock;
+       /* Transfer state (TRANSFERING/FLUSHING/FINISHED) */
+       int state;
+       /* Buffer. */
+       char buf[BUFFERSIZE];
+       /* Buffer used. */
+       size_t bufuse;
+       /* Name of source. */
+       const char *src_name;
+       /* Name of destination. */
+       const char *dest_name;
+};
+
+/* Closes the target (for writing) if transfer has finished. */
+static void udt_close_if_finished(struct unidirectional_transfer *t)
+{
+       if (STATE_NEEDS_CLOSING(t->state) && !t->bufuse) {
+               t->state = SSTATE_FINISHED;
+               if (t->dest_is_sock)
+                       shutdown(t->dest, SHUT_WR);
+               else
+                       close(t->dest);
+               transfer_debug("Closed %s.", t->dest_name);
+       }
+}
+
+/*
+ * Tries to read read data from source into buffer. If buffer is full,
+ * no data is read. Returns 0 on success, -1 on error.
+ */
+static int udt_do_read(struct unidirectional_transfer *t)
+{
+       ssize_t bytes;
+
+       if (t->bufuse == BUFFERSIZE)
+               return 0;       /* No space for more. */
+
+       transfer_debug("%s is readable", t->src_name);
+       bytes = read(t->src, t->buf + t->bufuse, BUFFERSIZE - t->bufuse);
+       if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+               errno != EINTR) {
+               error("read(%s) failed: %s", t->src_name, strerror(errno));
+               return -1;
+       } else if (bytes == 0) {
+               transfer_debug("%s EOF (with %i bytes in buffer)",
+                       t->src_name, t->bufuse);
+               t->state = SSTATE_FLUSHING;
+       } else if (bytes > 0) {
+               t->bufuse += bytes;
+               transfer_debug("Read %i bytes from %s (buffer now at %i)",
+                       (int)bytes, t->src_name, (int)t->bufuse);
+       }
+       return 0;
+}
+
+/* Tries to write data from buffer into destination. If buffer is empty,
+ * no data is written. Returns 0 on success, -1 on error.
+ */
+static int udt_do_write(struct unidirectional_transfer *t)
+{
+       ssize_t bytes;
+
+       if (t->bufuse == 0)
+               return 0;       /* Nothing to write. */
+
+       transfer_debug("%s is writable", t->dest_name);
+       bytes = write(t->dest, t->buf, t->bufuse);
+       if (bytes < 0 && errno != EWOULDBLOCK && errno != EAGAIN &&
+               errno != EINTR) {
+               error("write(%s) failed: %s", t->dest_name, strerror(errno));
+               return -1;
+       } else if (bytes > 0) {
+               t->bufuse -= bytes;
+               if (t->bufuse)
+                       memmove(t->buf, t->buf + bytes, t->bufuse);
+               transfer_debug("Wrote %i bytes to %s (buffer now at %i)",
+                       (int)bytes, t->dest_name, (int)t->bufuse);
+       }
+       return 0;
+}
+
+
+/* State of bidirectional transfer loop. */
+struct bidirectional_transfer_state {
+       /* Direction from program to git. */
+       struct unidirectional_transfer ptg;
+       /* Direction from git to program. */
+       struct unidirectional_transfer gtp;
+};
+
+static void *udt_copy_task_routine(void *udt)
+{
+       struct unidirectional_transfer *t = (struct unidirectional_transfer *)udt;
+       while (t->state != SSTATE_FINISHED) {
+               if (STATE_NEEDS_READING(t->state))
+                       if (udt_do_read(t))
+                               return NULL;
+               if (STATE_NEEDS_WRITING(t->state))
+                       if (udt_do_write(t))
+                               return NULL;
+               if (STATE_NEEDS_CLOSING(t->state))
+                       udt_close_if_finished(t);
+       }
+       return udt;     /* Just some non-NULL value. */
+}
+
+#ifndef NO_PTHREADS
+
+/*
+ * Join thread, with apporiate errors on failure. Name is name for the
+ * thread (for error messages). Returns 0 on success, 1 on failure.
+ */
+static int tloop_join(pthread_t thread, const char *name)
+{
+       int err;
+       void *tret;
+       err = pthread_join(thread, &tret);
+       if (!tret) {
+               error("%s thread failed", name);
+               return 1;
+       }
+       if (err) {
+               error("%s thread failed to join: %s", name, strerror(err));
+               return 1;
+       }
+       return 0;
+}
+
+/*
+ * Spawn the transfer tasks and then wait for them. Returns 0 on success,
+ * -1 on failure.
+ */
+static int tloop_spawnwait_tasks(struct bidirectional_transfer_state *s)
+{
+       pthread_t gtp_thread;
+       pthread_t ptg_thread;
+       int err;
+       int ret = 0;
+       err = pthread_create(&gtp_thread, NULL, udt_copy_task_routine,
+               &s->gtp);
+       if (err)
+               die("Can't start thread for copying data: %s", strerror(err));
+       err = pthread_create(&ptg_thread, NULL, udt_copy_task_routine,
+               &s->ptg);
+       if (err)
+               die("Can't start thread for copying data: %s", strerror(err));
+
+       ret |= tloop_join(gtp_thread, "Git to program copy");
+       ret |= tloop_join(ptg_thread, "Program to git copy");
+       return ret;
+}
+#else
+
+/* Close the source and target (for writing) for transfer. */
+static void udt_kill_transfer(struct unidirectional_transfer *t)
+{
+       t->state = SSTATE_FINISHED;
+       /*
+        * Socket read end left open isn't a disaster if nobody
+        * attempts to read from it (mingw compat headers do not
+        * have SHUT_RD)...
+        *
+        * We can't fully close the socket since otherwise gtp
+        * task would first close the socket it sends data to
+        * while closing the ptg file descriptors.
+        */
+       if (!t->src_is_sock)
+               close(t->src);
+       if (t->dest_is_sock)
+               shutdown(t->dest, SHUT_WR);
+       else
+               close(t->dest);
+}
+
+/*
+ * Join process, with apporiate errors on failure. Name is name for the
+ * process (for error messages). Returns 0 on success, 1 on failure.
+ */
+static int tloop_join(pid_t pid, const char *name)
+{
+       int tret;
+       if (waitpid(pid, &tret, 0) < 0) {
+               error("%s process failed to wait: %s", name, strerror(errno));
+               return 1;
+       }
+       if (!WIFEXITED(tret) || WEXITSTATUS(tret)) {
+               error("%s process failed", name);
+               return 1;
+       }
+       return 0;
+}
+
+/*
+ * Spawn the transfer tasks and then wait for them. Returns 0 on success,
+ * -1 on failure.
+ */
+static int tloop_spawnwait_tasks(struct bidirectional_transfer_state *s)
+{
+       pid_t pid1, pid2;
+       int ret = 0;
+
+       /* Fork thread #1: git to program. */
+       pid1 = fork();
+       if (pid1 < 0)
+               die_errno("Can't start thread for copying data");
+       else if (pid1 == 0) {
+               udt_kill_transfer(&s->ptg);
+               exit(udt_copy_task_routine(&s->gtp) ? 0 : 1);
+       }
+
+       /* Fork thread #2: program to git. */
+       pid2 = fork();
+       if (pid2 < 0)
+               die_errno("Can't start thread for copying data");
+       else if (pid2 == 0) {
+               udt_kill_transfer(&s->gtp);
+               exit(udt_copy_task_routine(&s->ptg) ? 0 : 1);
+       }
+
+       /*
+        * Close both streams in parent as to not interfere with
+        * end of file detection and wait for both tasks to finish.
+        */
+       udt_kill_transfer(&s->gtp);
+       udt_kill_transfer(&s->ptg);
+       ret |= tloop_join(pid1, "Git to program copy");
+       ret |= tloop_join(pid2, "Program to git copy");
+       return ret;
+}
+#endif
+
+/*
+ * Copies data from stdin to output and from input to stdout simultaneously.
+ * Additionally filtering through given filter. If filter is NULL, uses
+ * identity filter.
+ */
+int bidirectional_transfer_loop(int input, int output)
+{
+       struct bidirectional_transfer_state state;
+
+       /* Fill the state fields. */
+       state.ptg.src = input;
+       state.ptg.dest = 1;
+       state.ptg.src_is_sock = (input == output);
+       state.ptg.dest_is_sock = 0;
+       state.ptg.state = SSTATE_TRANSFERING;
+       state.ptg.bufuse = 0;
+       state.ptg.src_name = "remote input";
+       state.ptg.dest_name = "stdout";
+
+       state.gtp.src = 0;
+       state.gtp.dest = output;
+       state.gtp.src_is_sock = 0;
+       state.gtp.dest_is_sock = (input == output);
+       state.gtp.state = SSTATE_TRANSFERING;
+       state.gtp.bufuse = 0;
+       state.gtp.src_name = "stdin";
+       state.gtp.dest_name = "remote output";
+
+       return tloop_spawnwait_tasks(&state);
+}