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fetch-pack: do not take shallow lock unnecessarily

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When fetching using protocol v2, the remote may send a "shallow-info"
section if the client is shallow. If so, Git as the client currently
takes the shallow file lock, even if the "shallow-info" section is
empty.

This is not a problem except that Git does not support taking the
shallow file lock after modifying the shallow file, because
is_repository_shallow() stores information that is never cleared. And
this take-after-modify occurs when Git does a tag-following fetch from a
shallow repository on a transport that does not support tag following
(since in this case, 2 fetches are performed).

To solve this issue, take the shallow file lock (and perform all other
shallow processing) only if the "shallow-info" section is non-empty;
otherwise, behave as if it were empty.

A full solution (probably, ensuring that any action of committing
shallow file locks also includes clearing the information stored by
is_repository_shallow()) would solve the issue without need for this
patch, but this patch is independently useful (as an optimization to
prevent writing a file in an unnecessary case), hence why I wrote it. I
have included a NEEDSWORK outlining the full solution.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jonathan Tan
2019-01-10 11:36:45 -08:00
committed by Junio C Hamano
parent ecbdaf0899
commit bd0b42aed3
3 changed files with 34 additions and 2 deletions
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11
fetch-pack.c
View File

@ -1232,6 +1232,8 @@ static int process_acks(struct fetch_negotiator *negotiator,
static void receive_shallow_info(struct fetch_pack_args *args,
struct packet_reader *reader)
{
int line_received = 0;
process_section_header(reader, "shallow-info", 0);
while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
const char *arg;
@ -1241,6 +1243,7 @@ static void receive_shallow_info(struct fetch_pack_args *args,
if (get_oid_hex(arg, &oid))
die(_("invalid shallow line: %s"), reader->line);
register_shallow(the_repository, &oid);
line_received = 1;
continue;
}
if (skip_prefix(reader->line, "unshallow ", &arg)) {
@ -1253,6 +1256,7 @@ static void receive_shallow_info(struct fetch_pack_args *args,
die(_("error in object: %s"), reader->line);
if (unregister_shallow(&oid))
die(_("no shallow found: %s"), reader->line);
line_received = 1;
continue;
}
die(_("expected shallow/unshallow, got %s"), reader->line);
@ -1262,8 +1266,11 @@ static void receive_shallow_info(struct fetch_pack_args *args,
reader->status != PACKET_READ_DELIM)
die(_("error processing shallow info: %d"), reader->status);
setup_alternate_shallow(&shallow_lock, &alternate_shallow_file, NULL);
args->deepen = 1;
if (line_received) {
setup_alternate_shallow(&shallow_lock, &alternate_shallow_file,
NULL);
args->deepen = 1;
}
}
static void receive_wanted_refs(struct packet_reader *reader,