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Add support for external programs for handling native fetches
transport_get() can call transport_native_helper_init() to have list and fetch-ref operations handled by running a separate program as: git remote-<something> <remote> [<url>] This program then accepts, on its stdin, "list" and "fetch <hex> <name>" commands; the former prints out a list of available refs and either their hashes or what they are symrefs to, while the latter fetches them into the local object database and prints a newline when done. Signed-off-by: Daniel Barkalow <[email protected]> Signed-off-by: Junio C Hamano <[email protected]>
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‎Documentation/git-remote-helpers.txt

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git-remote-helpers(1)
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=====================
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NAME
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----
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git-remote-helpers - Helper programs for interoperation with remote git
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SYNOPSIS
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--------
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'git remote-<transport>' <remote>
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DESCRIPTION
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-----------
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These programs are normally not used directly by end users, but are
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invoked by various git programs that interact with remote repositories
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when the repository they would operate on will be accessed using
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transport code not linked into the main git binary. Various particular
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helper programs will behave as documented here.
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COMMANDS
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--------
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Commands are given by the caller on the helper's standard input, one per line.
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'capabilities'::
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Lists the capabilities of the helper, one per line, ending
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with a blank line.
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'list'::
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Lists the refs, one per line, in the format "<value> <name>
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[<attr> ...]". The value may be a hex sha1 hash, "@<dest>" for
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a symref, or "?" to indicate that the helper could not get the
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value of the ref. A space-separated list of attributes follows
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the name; unrecognized attributes are ignored. After the
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complete list, outputs a blank line.
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'fetch' <sha1> <name>::
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Fetches the given object, writing the necessary objects to the
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database. Outputs a blank line when the fetch is
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complete. Only objects which were reported in the ref list
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with a sha1 may be fetched this way.
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Supported if the helper has the "fetch" capability.
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If a fatal error occurs, the program writes the error message to
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stderr and exits. The caller should expect that a suitable error
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message has been printed if the child closes the connection without
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completing a valid response for the current command.
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Additional commands may be supported, as may be determined from
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capabilities reported by the helper.
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CAPABILITIES
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------------
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'fetch'::
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This helper supports the 'fetch' command.
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REF LIST ATTRIBUTES
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-------------------
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None are defined yet, but the caller must accept any which are supplied.
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Documentation
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-------------
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Documentation by Daniel Barkalow.
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GIT
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---
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Part of the linkgit:git[1] suite

‎Makefile

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@@ -549,6 +549,7 @@ LIB_OBJS += symlinks.o
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LIB_OBJS += tag.o
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LIB_OBJS += trace.o
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LIB_OBJS += transport.o
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LIB_OBJS += transport-helper.o
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LIB_OBJS += tree-diff.o
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LIB_OBJS += tree.o
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LIB_OBJS += tree-walk.o

‎transport-helper.c

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#include "cache.h"
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#include "transport.h"
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#include "run-command.h"
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#include "commit.h"
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#include "diff.h"
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#include "revision.h"
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struct helper_data
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{
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const char *name;
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struct child_process *helper;
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unsigned fetch : 1;
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};
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static struct child_process *get_helper(struct transport *transport)
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{
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struct helper_data *data = transport->data;
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struct strbuf buf = STRBUF_INIT;
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struct child_process *helper;
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FILE *file;
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if (data->helper)
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return data->helper;
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helper = xcalloc(1, sizeof(*helper));
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helper->in = -1;
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helper->out = -1;
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helper->err = 0;
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helper->argv = xcalloc(4, sizeof(*helper->argv));
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strbuf_addf(&buf, "remote-%s", data->name);
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helper->argv[0] = strbuf_detach(&buf, NULL);
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helper->argv[1] = transport->remote->name;
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helper->argv[2] = transport->url;
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helper->git_cmd = 1;
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if (start_command(helper))
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die("Unable to run helper: git %s", helper->argv[0]);
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data->helper = helper;
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write_in_full(data->helper->in, "capabilities\n", 13);
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file = fdopen(helper->out, "r");
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while (1) {
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if (strbuf_getline(&buf, file, '\n') == EOF)
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exit(128); /* child died, message supplied already */
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if (!*buf.buf)
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break;
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if (!strcmp(buf.buf, "fetch"))
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data->fetch = 1;
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}
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return data->helper;
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}
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static int disconnect_helper(struct transport *transport)
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{
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struct helper_data *data = transport->data;
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if (data->helper) {
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write_in_full(data->helper->in, "\n", 1);
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close(data->helper->in);
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finish_command(data->helper);
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free((char *)data->helper->argv[0]);
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free(data->helper->argv);
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free(data->helper);
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data->helper = NULL;
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}
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return 0;
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}
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static int fetch_with_fetch(struct transport *transport,
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int nr_heads, const struct ref **to_fetch)
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{
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struct child_process *helper = get_helper(transport);
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FILE *file = fdopen(helper->out, "r");
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int i;
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struct strbuf buf = STRBUF_INIT;
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for (i = 0; i < nr_heads; i++) {
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struct ref *posn = to_fetch[i];
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if (posn->status & REF_STATUS_UPTODATE)
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continue;
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write_in_full(helper->in, "fetch ", 6);
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write_in_full(helper->in, sha1_to_hex(posn->old_sha1), 40);
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write_in_full(helper->in, " ", 1);
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write_in_full(helper->in, posn->name, strlen(posn->name));
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write_in_full(helper->in, "\n", 1);
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if (strbuf_getline(&buf, file, '\n') == EOF)
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exit(128); /* child died, message supplied already */
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}
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return 0;
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}
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static int fetch(struct transport *transport,
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int nr_heads, const struct ref **to_fetch)
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{
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struct helper_data *data = transport->data;
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int i, count;
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count = 0;
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for (i = 0; i < nr_heads; i++)
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if (!(to_fetch[i]->status & REF_STATUS_UPTODATE))
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count++;
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if (!count)
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return 0;
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if (data->fetch)
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return fetch_with_fetch(transport, nr_heads, to_fetch);
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return -1;
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}
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static struct ref *get_refs_list(struct transport *transport, int for_push)
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{
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struct child_process *helper;
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struct ref *ret = NULL;
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struct ref **tail = &ret;
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struct ref *posn;
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struct strbuf buf = STRBUF_INIT;
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FILE *file;
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helper = get_helper(transport);
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write_in_full(helper->in, "list\n", 5);
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file = fdopen(helper->out, "r");
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while (1) {
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char *eov, *eon;
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if (strbuf_getline(&buf, file, '\n') == EOF)
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exit(128); /* child died, message supplied already */
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if (!*buf.buf)
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break;
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eov = strchr(buf.buf, ' ');
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if (!eov)
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die("Malformed response in ref list: %s", buf.buf);
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eon = strchr(eov + 1, ' ');
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*eov = '\0';
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if (eon)
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*eon = '\0';
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*tail = alloc_ref(eov + 1);
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if (buf.buf[0] == '@')
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(*tail)->symref = xstrdup(buf.buf + 1);
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else if (buf.buf[0] != '?')
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get_sha1_hex(buf.buf, (*tail)->old_sha1);
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tail = &((*tail)->next);
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}
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strbuf_release(&buf);
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for (posn = ret; posn; posn = posn->next)
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resolve_remote_symref(posn, ret);
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return ret;
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}
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int transport_helper_init(struct transport *transport)
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{
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struct helper_data *data = xcalloc(sizeof(*data), 1);
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char *eom = strchr(transport->url, ':');
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if (!eom)
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return -1;
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data->name = xstrndup(transport->url, eom - transport->url);
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transport->data = data;
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transport->get_refs_list = get_refs_list;
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transport->fetch = fetch;
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transport->disconnect = disconnect_helper;
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return 0;
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}

‎transport.h

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int transport_disconnect(struct transport *transport);
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char *transport_anonymize_url(const char *url);
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/* Transport methods defined outside transport.c */
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int transport_helper_init(struct transport *transport);
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#endif

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