[PATCH 5/5] 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>
---
builtin/fetch.c | 13 +++++++++++++
transport.c | 2 ++
transport.h | 6 ++++++
3 files changed, 21 insertions(+)
Show changes to 3 files +21 −0
builtin/fetch.c, transport.c, transport.h
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 0b21f07..57ab7e4 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -37,6 +37,7 @@ static const char *depth;
static const char *upload_pack;
static struct strbuf default_rla = STRBUF_INIT;
static struct transport *gtransport;
+static struct transport *gsecondary;
static const char *submodule_prefix = "";
static const char *recurse_submodules_default;
@@ -97,6 +98,8 @@ static void unlock_pack(void)
{
if (gtransport)
transport_unlock_pack(gtransport);
+ if (gsecondary)
+ transport_unlock_pack(gsecondary);
}
static void unlock_pack_on_signal(int signo)
@@ -747,9 +750,19 @@ struct transport *prepare_transport(struct remote *remote)
static void backfill_tags(struct transport *transport, struct ref *ref_map)
{
+ if (transport->cannot_reuse) {
+ gsecondary = prepare_transport(transport->remote);
+ transport = gsecondary;
+ }
+
transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, NULL);
transport_set_option(transport, TRANS_OPT_DEPTH, "0");
fetch_refs(transport, ref_map);
+
+ if (gsecondary) {
+ transport_disconnect(gsecondary);
+ gsecondary = NULL;
+ }
}
static int do_fetch(struct transport *transport,
diff --git a/transport.c b/transport.c
index e15db98..de25588 100644
--- a/transport.c
+++ b/transport.c
@@ -875,6 +875,8 @@ void transport_take_over(struct transport *transport,
transport->push_refs = git_transport_push;
transport->disconnect = disconnect_git;
transport->smart_options = &(data->options);
+
+ transport->cannot_reuse = 1;
}
static int is_local(const char *url)
diff --git a/transport.h b/transport.h
index ea70ea7..96e0ede 100644
--- a/transport.h
+++ b/transport.h
@@ -27,6 +27,12 @@ struct transport {
*/
unsigned got_remote_refs : 1;
+ /*
+ * Transports that call take-over destroys the data specific to
+ * the transport type while doing so, and cannot be reused.
+ */
+ unsigned cannot_reuse : 1;
+
/**
* Returns 0 if successful, positive if the option is not
* recognized or is inapplicable, and negative if the option
--
1.8.4-rc1-210-gf6d87e2
Junio C Hamano