mirror of
https://github.com/git/git
synced 2024-08-24 18:26:02 +00:00
a85b377d04
While signed tags and commits assert that the objects thusly signed
came from you, who signed these objects, there is not a good way to
assert that you wanted to have a particular object at the tip of a
particular branch. My signing v2.0.1 tag only means I want to call
the version v2.0.1, and it does not mean I want to push it out to my
'master' branch---it is likely that I only want it in 'maint', so
the signature on the object alone is insufficient.
The only assurance to you that 'maint' points at what I wanted to
place there comes from your trust on the hosting site and my
authentication with it, which cannot easily audited later.
Introduce a mechanism that allows you to sign a "push certificate"
(for the lack of better name) every time you push, asserting that
what object you are pushing to update which ref that used to point
at what other object. Think of it as a cryptographic protection for
ref updates, similar to signed tags/commits but working on an
orthogonal axis.
The basic flow based on this mechanism goes like this:
1. You push out your work with "git push --signed".
2. The sending side learns where the remote refs are as usual,
together with what protocol extension the receiving end
supports. If the receiving end does not advertise the protocol
extension "push-cert", an attempt to "git push --signed" fails.
Otherwise, a text file, that looks like the following, is
prepared in core:
certificate version 0.1
pusher Junio C Hamano <gitster@pobox.com> 1315427886 -0700
7339ca65... 21580ecb... refs/heads/master
3793ac56... 12850bec... refs/heads/next
The file begins with a few header lines, which may grow as we
gain more experience. The 'pusher' header records the name of
the signer (the value of user.signingkey configuration variable,
falling back to GIT_COMMITTER_{NAME|EMAIL}) and the time of the
certificate generation. After the header, a blank line follows,
followed by a copy of the protocol message lines.
Each line shows the old and the new object name at the tip of
the ref this push tries to update, in the way identical to how
the underlying "git push" protocol exchange tells the ref
updates to the receiving end (by recording the "old" object
name, the push certificate also protects against replaying). It
is expected that new command packet types other than the
old-new-refname kind will be included in push certificate in the
same way as would appear in the plain vanilla command packets in
unsigned pushes.
The user then is asked to sign this push certificate using GPG,
formatted in a way similar to how signed tag objects are signed,
and the result is sent to the other side (i.e. receive-pack).
In the protocol exchange, this step comes immediately before the
sender tells what the result of the push should be, which in
turn comes before it sends the pack data.
3. When the receiving end sees a push certificate, the certificate
is written out as a blob. The pre-receive hook can learn about
the certificate by checking GIT_PUSH_CERT environment variable,
which, if present, tells the object name of this blob, and make
the decision to allow or reject this push. Additionally, the
post-receive hook can also look at the certificate, which may be
a good place to log all the received certificates for later
audits.
Because a push certificate carry the same information as the usual
command packets in the protocol exchange, we can omit the latter
when a push certificate is in use and reduce the protocol overhead.
This however is not included in this patch to make it easier to
review (in other words, the series at this step should never be
released without the remainder of the series, as it implements an
interim protocol that will be incompatible with the final one).
As such, the documentation update for the protocol is left out of
this step.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
458 lines
11 KiB
C
458 lines
11 KiB
C
#include "builtin.h"
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#include "commit.h"
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#include "refs.h"
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#include "pkt-line.h"
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#include "sideband.h"
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#include "run-command.h"
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#include "remote.h"
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#include "connect.h"
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#include "send-pack.h"
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#include "quote.h"
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#include "transport.h"
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#include "version.h"
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#include "sha1-array.h"
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#include "gpg-interface.h"
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static int feed_object(const unsigned char *sha1, int fd, int negative)
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{
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char buf[42];
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if (negative && !has_sha1_file(sha1))
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return 1;
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memcpy(buf + negative, sha1_to_hex(sha1), 40);
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if (negative)
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buf[0] = '^';
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buf[40 + negative] = '\n';
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return write_or_whine(fd, buf, 41 + negative, "send-pack: send refs");
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}
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/*
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* Make a pack stream and spit it out into file descriptor fd
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*/
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static int pack_objects(int fd, struct ref *refs, struct sha1_array *extra, struct send_pack_args *args)
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{
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/*
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* The child becomes pack-objects --revs; we feed
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* the revision parameters to it via its stdin and
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* let its stdout go back to the other end.
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*/
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const char *argv[] = {
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"pack-objects",
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"--all-progress-implied",
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"--revs",
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"--stdout",
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NULL,
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NULL,
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NULL,
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NULL,
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NULL,
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};
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struct child_process po;
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int i;
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i = 4;
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if (args->use_thin_pack)
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argv[i++] = "--thin";
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if (args->use_ofs_delta)
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argv[i++] = "--delta-base-offset";
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if (args->quiet || !args->progress)
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argv[i++] = "-q";
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if (args->progress)
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argv[i++] = "--progress";
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memset(&po, 0, sizeof(po));
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po.argv = argv;
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po.in = -1;
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po.out = args->stateless_rpc ? -1 : fd;
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po.git_cmd = 1;
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if (start_command(&po))
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die_errno("git pack-objects failed");
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/*
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* We feed the pack-objects we just spawned with revision
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* parameters by writing to the pipe.
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*/
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for (i = 0; i < extra->nr; i++)
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if (!feed_object(extra->sha1[i], po.in, 1))
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break;
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while (refs) {
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if (!is_null_sha1(refs->old_sha1) &&
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!feed_object(refs->old_sha1, po.in, 1))
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break;
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if (!is_null_sha1(refs->new_sha1) &&
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!feed_object(refs->new_sha1, po.in, 0))
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break;
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refs = refs->next;
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}
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close(po.in);
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if (args->stateless_rpc) {
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char *buf = xmalloc(LARGE_PACKET_MAX);
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while (1) {
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ssize_t n = xread(po.out, buf, LARGE_PACKET_MAX);
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if (n <= 0)
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break;
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send_sideband(fd, -1, buf, n, LARGE_PACKET_MAX);
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}
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free(buf);
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close(po.out);
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po.out = -1;
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}
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if (finish_command(&po))
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return -1;
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return 0;
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}
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static int receive_status(int in, struct ref *refs)
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{
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struct ref *hint;
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int ret = 0;
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char *line = packet_read_line(in, NULL);
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if (!starts_with(line, "unpack "))
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return error("did not receive remote status");
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if (strcmp(line, "unpack ok")) {
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error("unpack failed: %s", line + 7);
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ret = -1;
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}
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hint = NULL;
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while (1) {
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char *refname;
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char *msg;
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line = packet_read_line(in, NULL);
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if (!line)
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break;
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if (!starts_with(line, "ok ") && !starts_with(line, "ng ")) {
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error("invalid ref status from remote: %s", line);
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ret = -1;
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break;
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}
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refname = line + 3;
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msg = strchr(refname, ' ');
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if (msg)
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*msg++ = '\0';
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/* first try searching at our hint, falling back to all refs */
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if (hint)
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hint = find_ref_by_name(hint, refname);
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if (!hint)
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hint = find_ref_by_name(refs, refname);
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if (!hint) {
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warning("remote reported status on unknown ref: %s",
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refname);
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continue;
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}
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if (hint->status != REF_STATUS_EXPECTING_REPORT) {
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warning("remote reported status on unexpected ref: %s",
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refname);
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continue;
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}
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if (line[0] == 'o' && line[1] == 'k')
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hint->status = REF_STATUS_OK;
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else {
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hint->status = REF_STATUS_REMOTE_REJECT;
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ret = -1;
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}
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if (msg)
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hint->remote_status = xstrdup(msg);
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/* start our next search from the next ref */
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hint = hint->next;
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}
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return ret;
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}
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static int sideband_demux(int in, int out, void *data)
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{
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int *fd = data, ret;
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#ifdef NO_PTHREADS
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close(fd[1]);
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#endif
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ret = recv_sideband("send-pack", fd[0], out);
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close(out);
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return ret;
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}
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static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
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{
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struct strbuf *sb = cb;
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if (graft->nr_parent == -1)
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packet_buf_write(sb, "shallow %s\n", sha1_to_hex(graft->sha1));
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return 0;
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}
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static void advertise_shallow_grafts_buf(struct strbuf *sb)
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{
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if (!is_repository_shallow())
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return;
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for_each_commit_graft(advertise_shallow_grafts_cb, sb);
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}
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static int ref_update_to_be_sent(const struct ref *ref, const struct send_pack_args *args)
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{
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if (!ref->peer_ref && !args->send_mirror)
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return 0;
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/* Check for statuses set by set_ref_status_for_push() */
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switch (ref->status) {
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case REF_STATUS_REJECT_NONFASTFORWARD:
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case REF_STATUS_REJECT_ALREADY_EXISTS:
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case REF_STATUS_REJECT_FETCH_FIRST:
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case REF_STATUS_REJECT_NEEDS_FORCE:
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case REF_STATUS_REJECT_STALE:
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case REF_STATUS_REJECT_NODELETE:
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case REF_STATUS_UPTODATE:
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return 0;
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default:
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return 1;
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}
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}
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/*
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* the beginning of the next line, or the end of buffer.
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*
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* NEEDSWORK: perhaps move this to git-compat-util.h or somewhere and
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* convert many similar uses found by "git grep -A4 memchr".
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*/
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static const char *next_line(const char *line, size_t len)
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{
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const char *nl = memchr(line, '\n', len);
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if (!nl)
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return line + len; /* incomplete line */
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return nl + 1;
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}
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static void generate_push_cert(struct strbuf *req_buf,
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const struct ref *remote_refs,
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struct send_pack_args *args)
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{
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const struct ref *ref;
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char stamp[60];
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char *signing_key = xstrdup(get_signing_key());
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const char *cp, *np;
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struct strbuf cert = STRBUF_INIT;
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int update_seen = 0;
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datestamp(stamp, sizeof(stamp));
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strbuf_addf(&cert, "certificate version 0.1\n");
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strbuf_addf(&cert, "pusher %s %s\n", signing_key, stamp);
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strbuf_addstr(&cert, "\n");
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for (ref = remote_refs; ref; ref = ref->next) {
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if (!ref_update_to_be_sent(ref, args))
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continue;
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update_seen = 1;
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strbuf_addf(&cert, "%s %s %s\n",
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sha1_to_hex(ref->old_sha1),
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sha1_to_hex(ref->new_sha1),
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ref->name);
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}
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if (!update_seen)
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goto free_return;
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if (sign_buffer(&cert, &cert, signing_key))
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die(_("failed to sign the push certificate"));
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packet_buf_write(req_buf, "push-cert\n");
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for (cp = cert.buf; cp < cert.buf + cert.len; cp = np) {
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np = next_line(cp, cert.buf + cert.len - cp);
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packet_buf_write(req_buf,
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"%.*s", (int)(np - cp), cp);
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}
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packet_buf_write(req_buf, "push-cert-end\n");
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free_return:
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free(signing_key);
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strbuf_release(&cert);
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}
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int send_pack(struct send_pack_args *args,
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int fd[], struct child_process *conn,
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struct ref *remote_refs,
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struct sha1_array *extra_have)
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{
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int in = fd[0];
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int out = fd[1];
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struct strbuf req_buf = STRBUF_INIT;
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struct strbuf cap_buf = STRBUF_INIT;
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struct ref *ref;
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int need_pack_data = 0;
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int allow_deleting_refs = 0;
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int status_report = 0;
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int use_sideband = 0;
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int quiet_supported = 0;
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int agent_supported = 0;
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unsigned cmds_sent = 0;
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int ret;
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struct async demux;
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/* Does the other end support the reporting? */
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if (server_supports("report-status"))
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status_report = 1;
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if (server_supports("delete-refs"))
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allow_deleting_refs = 1;
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if (server_supports("ofs-delta"))
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args->use_ofs_delta = 1;
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if (server_supports("side-band-64k"))
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use_sideband = 1;
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if (server_supports("quiet"))
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quiet_supported = 1;
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if (server_supports("agent"))
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agent_supported = 1;
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if (server_supports("no-thin"))
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args->use_thin_pack = 0;
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if (args->push_cert && !server_supports("push-cert"))
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die(_("the receiving end does not support --signed push"));
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if (!remote_refs) {
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fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
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"Perhaps you should specify a branch such as 'master'.\n");
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return 0;
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}
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if (status_report)
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strbuf_addstr(&cap_buf, " report-status");
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if (use_sideband)
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strbuf_addstr(&cap_buf, " side-band-64k");
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if (quiet_supported && (args->quiet || !args->progress))
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strbuf_addstr(&cap_buf, " quiet");
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if (agent_supported)
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strbuf_addf(&cap_buf, " agent=%s", git_user_agent_sanitized());
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/*
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* NEEDSWORK: why does delete-refs have to be so specific to
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* send-pack machinery that set_ref_status_for_push() cannot
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* set this bit for us???
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*/
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for (ref = remote_refs; ref; ref = ref->next)
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if (ref->deletion && !allow_deleting_refs)
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ref->status = REF_STATUS_REJECT_NODELETE;
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if (!args->dry_run)
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advertise_shallow_grafts_buf(&req_buf);
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if (!args->dry_run && args->push_cert)
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generate_push_cert(&req_buf, remote_refs, args);
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/*
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* Clear the status for each ref and see if we need to send
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* the pack data.
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*/
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for (ref = remote_refs; ref; ref = ref->next) {
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if (!ref_update_to_be_sent(ref, args))
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continue;
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if (!ref->deletion)
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need_pack_data = 1;
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if (args->dry_run || !status_report)
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ref->status = REF_STATUS_OK;
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else
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ref->status = REF_STATUS_EXPECTING_REPORT;
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}
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/*
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* Finally, tell the other end!
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*/
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for (ref = remote_refs; ref; ref = ref->next) {
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char *old_hex, *new_hex;
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if (args->dry_run)
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continue;
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if (!ref_update_to_be_sent(ref, args))
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continue;
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old_hex = sha1_to_hex(ref->old_sha1);
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new_hex = sha1_to_hex(ref->new_sha1);
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if (!cmds_sent) {
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packet_buf_write(&req_buf,
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"%s %s %s%c%s",
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old_hex, new_hex, ref->name, 0,
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cap_buf.buf);
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cmds_sent = 1;
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} else {
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packet_buf_write(&req_buf, "%s %s %s",
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old_hex, new_hex, ref->name);
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}
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}
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if (args->stateless_rpc) {
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if (!args->dry_run && (cmds_sent || is_repository_shallow())) {
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packet_buf_flush(&req_buf);
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send_sideband(out, -1, req_buf.buf, req_buf.len, LARGE_PACKET_MAX);
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}
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} else {
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write_or_die(out, req_buf.buf, req_buf.len);
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packet_flush(out);
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}
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strbuf_release(&req_buf);
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strbuf_release(&cap_buf);
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if (use_sideband && cmds_sent) {
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memset(&demux, 0, sizeof(demux));
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demux.proc = sideband_demux;
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demux.data = fd;
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demux.out = -1;
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if (start_async(&demux))
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die("send-pack: unable to fork off sideband demultiplexer");
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in = demux.out;
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}
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if (need_pack_data && cmds_sent) {
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if (pack_objects(out, remote_refs, extra_have, args) < 0) {
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for (ref = remote_refs; ref; ref = ref->next)
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ref->status = REF_STATUS_NONE;
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if (args->stateless_rpc)
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close(out);
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if (git_connection_is_socket(conn))
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shutdown(fd[0], SHUT_WR);
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if (use_sideband)
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finish_async(&demux);
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fd[1] = -1;
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return -1;
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}
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if (!args->stateless_rpc)
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/* Closed by pack_objects() via start_command() */
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fd[1] = -1;
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}
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if (args->stateless_rpc && cmds_sent)
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packet_flush(out);
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if (status_report && cmds_sent)
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ret = receive_status(in, remote_refs);
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else
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ret = 0;
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if (args->stateless_rpc)
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packet_flush(out);
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if (use_sideband && cmds_sent) {
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if (finish_async(&demux)) {
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error("error in sideband demultiplexer");
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ret = -1;
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}
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close(demux.out);
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}
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if (ret < 0)
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return ret;
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if (args->porcelain)
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return 0;
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for (ref = remote_refs; ref; ref = ref->next) {
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switch (ref->status) {
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case REF_STATUS_NONE:
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case REF_STATUS_UPTODATE:
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case REF_STATUS_OK:
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break;
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default:
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return -1;
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}
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}
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return 0;
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}
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