@matheusbsbs / matheus-bagliano / commits / b26ed4305f

fetch: work around "transport-take-over" hack

A Git-aware "connect" transport allows the "transport_take_over" to redirect generic transport requests like fetch(), push_refs() and get_refs_list() to the native Git transport handling methods. The take-over process replaces transport->data with a fake data that these method implementations understand. While this hack works OK for a single request, it breaks when the transport needs to make more than one requests. transport->data that used to hold necessary information for the specific helper to work correctly is destroyed during the take-over process. One codepath that this matters is "git fetch" in auto-follow mode; when it does not get all the tags that ought to point at the history it got (which can be determined by looking at the peeled tags in the initial advertisement) from the primary transfer, it internally makes a second request to complete the fetch. Because "take-over" hack has already destroyed the data necessary to talk to the transport helper by the time this happens, the second request cannot make a request to the helper to make another connection to fetch these additional tags. Mark such a transport as "cannot_reuse", and use a separate transport to perform the backfill fetch in order to work around this breakage. Note that this problem does not manifest itself when running t5802, because our upload-pack gives you all the necessary auto-followed tags during the primary transfer. You would need to step through "git fetch" in a debugger, stop immediately after the primary transfer finishes and writes these auto-followed tags, remove the tag references and repack/prune the repository to convince the "find-non-local-tags" procedure that the primary transfer failed to give us all the necessary tags, and then let it continue, in order to trigger the bug in the secondary transfer this patch fixes. Signed-off-by: Junio C Hamano <gitster@pobox.com>

Junio C Hamano committed Aug 7, 2013 at 15:47 UTC b26ed4305f9e7043133e52990897afbbf1808d6d

3 files changed +21

builtin/fetch.c

+13

@@ -37,6 +37,7 @@ static const char *depth;

37 static const char *upload_pack;

38 static struct strbuf default_rla = STRBUF_INIT;

39 static struct transport *gtransport;

40 +static struct transport *gsecondary;

41 static const char *submodule_prefix = "";

42 static const char *recurse_submodules_default;

@@ -97,6 +98,8 @@ static void unlock_pack(void)

98 {

99 if (gtransport)

100 transport_unlock_pack(gtransport);

101 + if (gsecondary)

102 + transport_unlock_pack(gsecondary);

103 }

104

105 static void unlock_pack_on_signal(int signo)

@@ -747,9 +750,19 @@ struct transport *prepare_transport(struct remote *remote)

750

751 static void backfill_tags(struct transport *transport, struct ref *ref_map)

752 {

753 + if (transport->cannot_reuse) {

754 + gsecondary = prepare_transport(transport->remote);

755 + transport = gsecondary;

756 + }

757 +

758 transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, NULL);

759 transport_set_option(transport, TRANS_OPT_DEPTH, "0");

760 fetch_refs(transport, ref_map);

761 +

762 + if (gsecondary) {

763 + transport_disconnect(gsecondary);

764 + gsecondary = NULL;

765 + }

766 }

767

768 static int do_fetch(struct transport *transport,

transport.c

@@ -875,6 +875,8 @@ void transport_take_over(struct transport *transport,

875 transport->push_refs = git_transport_push;

876 transport->disconnect = disconnect_git;

877 transport->smart_options = &(data->options);

878 +

879 + transport->cannot_reuse = 1;

880 }

881

882 static int is_local(const char *url)

transport.h

@@ -27,6 +27,12 @@ struct transport {

27 */

28 unsigned got_remote_refs : 1;

30 + /*

31 + * Transports that call take-over destroys the data specific to

32 + * the transport type while doing so, and cannot be reused.

33 + */

34 + unsigned cannot_reuse : 1;

35 +

36 /**

37 * Returns 0 if successful, positive if the option is not

38 * recognized or is inapplicable, and negative if the option