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fetch-pack: do not take shallow lock unnecessarily 

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,

7
shallow.c
View File

@ -43,6 +43,13 @@ int register_shallow(struct repository *r, const struct object_id *oid)
int is_repository_shallow(struct repository *r)
{
/*
* NEEDSWORK: This function updates
* r->parsed_objects->{is_shallow,shallow_stat} as a side effect but
* there is no corresponding function to clear them when the shallow
* file is updated.
*/
FILE *fp;
char buf[1024];
const char *path = r->parsed_objects->alternate_shallow_file;

18
t/t5702-protocol-v2.sh
View File

@ -471,6 +471,24 @@ test_expect_success 'upload-pack respects client shallows' '
grep "fetch< version 2" trace
'
test_expect_success 'ensure that multiple fetches in same process from a shallow repo works' '
rm -rf server client trace &&
test_create_repo server &&
test_commit -C server one &&
test_commit -C server two &&
test_commit -C server three &&
git clone --shallow-exclude two "file://$(pwd)/server" client &&
git -C server tag -a -m "an annotated tag" twotag two &&
# Triggers tag following (thus, 2 fetches in one process)
GIT_TRACE_PACKET="$(pwd)/trace" git -C client -c protocol.version=2 \
fetch --shallow-exclude one origin &&
# Ensure that protocol v2 is used
grep "fetch< version 2" trace
'
# Test protocol v2 with 'http://' transport
#
. "$TEST_DIRECTORY"/lib-httpd.sh