pkt-line: support tracing verbatim pack contents

When debugging the pack protocol, it is sometimes useful to
store the verbatim pack that we sent or received on the
wire. Looking at the on-disk result is often not helpful for
a few reasons:

1. If the operation is a clone, we destroy the repo on
failure, leaving nothing on disk.

2. If the pack is small, we unpack it immediately, and the
full pack never hits the disk.

3. If we feed the pack to "index-pack --fix-thin", the
resulting pack has the extra delta bases added to it.

We already have a GIT_TRACE_PACKET mechanism for tracing
packets. Let's extend it with GIT_TRACE_PACKFILE to dump the
verbatim packfile.

There are a few other positive fallouts that come from
rearranging this code:

- We currently disable the packet trace after seeing the
PACK header, even though we may get human-readable lines
on other sidebands; now we include them in the trace.

- We currently try to print "PACK ..." in the trace to
indicate that the packfile has started. But because we
disable packet tracing, we never printed this line. We
will now do so.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 45b64a714097c4e462a7d990b2bc6ae607bd1e10..345366937dcf46384790aca79b96dfe10e0a00a5 100644 (file)
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -1000,9 +1000,20 @@ Unsetting the variable, or setting it to empty, "0" or
        Enables trace messages for all packets coming in or out of a
        given program. This can help with debugging object negotiation
        or other protocol issues. Tracing is turned off at a packet
        Enables trace messages for all packets coming in or out of a
        given program. This can help with debugging object negotiation
        or other protocol issues. Tracing is turned off at a packet

-       starting with "PACK".
+       starting with "PACK" (but see 'GIT_TRACE_PACKFILE' below).

        See 'GIT_TRACE' for available trace output options.
 
        See 'GIT_TRACE' for available trace output options.
 

+'GIT_TRACE_PACKFILE'::
+       Enables tracing of packfiles sent or received by a
+       given program. Unlike other trace output, this trace is
+       verbatim: no headers, and no quoting of binary data. You almost
+       certainly want to direct into a file (e.g.,
+       `GIT_TRACE_PACKFILE=/tmp/my.pack`) rather than displaying it on
+       the terminal or mixing it with other trace output.
++
+Note that this is currently only implemented for the client side
+of clones and fetches.
+

 'GIT_TRACE_PERFORMANCE'::
        Enables performance related trace messages, e.g. total execution
        time of each Git command.
 'GIT_TRACE_PERFORMANCE'::
        Enables performance related trace messages, e.g. total execution
        time of each Git command.

diff --git a/pkt-line.c b/pkt-line.c
index e75af023b6e458203fa8854eb8305308fc62f619..08a1427c0d4f6743182b235ec9d9c710c3c99b5b 100644 (file)
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -4,16 +4,51 @@
 char packet_buffer[LARGE_PACKET_MAX];
 static const char *packet_trace_prefix = "git";
 static struct trace_key trace_packet = TRACE_KEY_INIT(PACKET);
 char packet_buffer[LARGE_PACKET_MAX];
 static const char *packet_trace_prefix = "git";
 static struct trace_key trace_packet = TRACE_KEY_INIT(PACKET);

+static struct trace_key trace_pack = TRACE_KEY_INIT(PACKFILE);

 
 void packet_trace_identity(const char *prog)
 {
        packet_trace_prefix = xstrdup(prog);
 }
 
 
 void packet_trace_identity(const char *prog)
 {
        packet_trace_prefix = xstrdup(prog);
 }
 

+static int packet_trace_pack(const char *buf, unsigned int len, int sideband)
+{
+       if (!sideband) {
+               trace_verbatim(&trace_pack, buf, len);
+               return 1;
+       } else if (len && *buf == '\1') {
+               trace_verbatim(&trace_pack, buf + 1, len - 1);
+               return 1;
+       } else {
+               /* it's another non-pack sideband */
+               return 0;
+       }
+}
+

 static void packet_trace(const char *buf, unsigned int len, int write)
 {
        int i;
        struct strbuf out;
 static void packet_trace(const char *buf, unsigned int len, int write)
 {
        int i;
        struct strbuf out;

+       static int in_pack, sideband;
+
+       if (!trace_want(&trace_packet) && !trace_want(&trace_pack))
+               return;
+
+       if (in_pack) {
+               if (packet_trace_pack(buf, len, sideband))
+                       return;
+       } else if (starts_with(buf, "PACK") || starts_with(buf, "\1PACK")) {
+               in_pack = 1;
+               sideband = *buf == '\1';
+               packet_trace_pack(buf, len, sideband);
+
+               /*
+                * Make a note in the human-readable trace that the pack data
+                * started.
+                */
+               buf = "PACK ...";
+               len = strlen(buf);
+       }

 
        if (!trace_want(&trace_packet))
                return;
 
        if (!trace_want(&trace_packet))
                return;


@@ -24,21 +59,15 @@ static void packet_trace(const char *buf, unsigned int len, int write)
        strbuf_addf(&out, "packet: %12s%c ",
                    packet_trace_prefix, write ? '>' : '<');
 
        strbuf_addf(&out, "packet: %12s%c ",
                    packet_trace_prefix, write ? '>' : '<');
 

-       if (starts_with(buf, "PACK") || starts_with(buf, "\1PACK")) {
-               strbuf_addstr(&out, "PACK ...");
-               trace_disable(&trace_packet);
-       }
-       else {
-               /* XXX we should really handle printable utf8 */
-               for (i = 0; i < len; i++) {
-                       /* suppress newlines */
-                       if (buf[i] == '\n')
-                               continue;
-                       if (buf[i] >= 0x20 && buf[i] <= 0x7e)
-                               strbuf_addch(&out, buf[i]);
-                       else
-                               strbuf_addf(&out, "\\%o", buf[i]);
-               }
+       /* XXX we should really handle printable utf8 */
+       for (i = 0; i < len; i++) {
+               /* suppress newlines */
+               if (buf[i] == '\n')
+                       continue;
+               if (buf[i] >= 0x20 && buf[i] <= 0x7e)
+                       strbuf_addch(&out, buf[i]);
+               else
+                       strbuf_addf(&out, "\\%o", buf[i]);

        }
 
        strbuf_addch(&out, '\n');
        }
 
        strbuf_addch(&out, '\n');

diff --git a/t/t5601-clone.sh b/t/t5601-clone.sh
index bfdaf75966f7b8bb057e4db0b8791306f6e6a44f..9b34f3c615df5080085b5f8cf956d2bac099d9d4 100755 (executable)
--- a/t/t5601-clone.sh
+++ b/t/t5601-clone.sh
@@ -496,4 +496,11 @@ test_expect_success 'shallow clone locally' '
        ( cd ddsstt && git fsck )
 '
 
        ( cd ddsstt && git fsck )
 '
 

+test_expect_success 'GIT_TRACE_PACKFILE produces a usable pack' '
+       rm -rf dst.git &&
+       GIT_TRACE_PACKFILE=$PWD/tmp.pack git clone --no-local --bare src dst.git &&
+       git init --bare replay.git &&
+       git -C replay.git index-pack -v --stdin <tmp.pack
+'
+

 test_done
 test_done

diff --git a/trace.c b/trace.c
index 3c3bd8fc98742075d6adc673ed2abc4f7e715b62..7393926ebcd95404fe16cdd84e40fd4f1bb02f40 100644 (file)
--- a/trace.c
+++ b/trace.c
@@ -120,6 +120,13 @@ static int prepare_trace_line(const char *file, int line,
        return 1;
 }
 
        return 1;
 }
 

+void trace_verbatim(struct trace_key *key, const void *buf, unsigned len)
+{
+       if (!trace_want(key))
+               return;
+       write_or_whine_pipe(get_trace_fd(key), buf, len, err_msg);
+}
+

 static void print_trace_line(struct trace_key *key, struct strbuf *buf)
 {
        strbuf_complete_line(buf);
 static void print_trace_line(struct trace_key *key, struct strbuf *buf)
 {
        strbuf_complete_line(buf);

diff --git a/trace.h b/trace.h
index ae6a3329470cae428bb0864e51b14ea42078b182..179b249c597125ac8ad3ed2d0c0e6b00a94773eb 100644 (file)
--- a/trace.h
+++ b/trace.h
@@ -18,6 +18,7 @@ extern int trace_want(struct trace_key *key);
 extern void trace_disable(struct trace_key *key);
 extern uint64_t getnanotime(void);
 extern void trace_command_performance(const char **argv);
 extern void trace_disable(struct trace_key *key);
 extern uint64_t getnanotime(void);
 extern void trace_command_performance(const char **argv);

+extern void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);

 
 #ifndef HAVE_VARIADIC_MACROS
 
 
 #ifndef HAVE_VARIADIC_MACROS