fetch-pack: show clearer error message upon ERR

Currently, fetch-pack prints a confusing error message ("expected
ACK/NAK") when the server it's communicating with sends a pkt-line
starting with "ERR".  Replace it with a less confusing error message.

Also update the documentation describing the fetch-pack/upload-pack
protocol (pack-protocol.txt) to indicate that "ERR" can be sent in the
place of "ACK" or "NAK". In practice, this has been done for quite some
time by other Git implementations (e.g. JGit sends "want $id not valid")
and by Git itself (since commit bdb31ea: "upload-pack: report "not our
ref" to client", 2017-02-23) whenever a "want" line references an object
that it does not have. (This is uncommon, but can happen if a repository
is garbage-collected during a negotiation.)

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
index c59ac9936a89e5e195b9a75bd4fd5d64a2385ffa..5b0ba3ef20144d1676cedbd8435e7bffddcde2f7 100644 (file)
--- a/Documentation/technical/pack-protocol.txt
+++ b/Documentation/technical/pack-protocol.txt
@@ -351,14 +351,19 @@ ACK after 'done' if there is at least one common base and multi_ack or
 multi_ack_detailed is enabled. The server always sends NAK after 'done'
 if there is no common base found.
 
+Instead of 'ACK' or 'NAK', the server may send an error message (for
+example, if it does not recognize an object in a 'want' line received
+from the client).
+
 Then the server will start sending its packfile data.
 
 ----
-  server-response = *ack_multi ack / nak
+  server-response = *ack_multi ack / nak / error-line
   ack_multi       = PKT-LINE("ACK" SP obj-id ack_status)
   ack_status      = "continue" / "common" / "ready"
   ack             = PKT-LINE("ACK" SP obj-id)
   nak             = PKT-LINE("NAK")
+  error-line     =  PKT-LINE("ERR" SP explanation-text)
 ----
 
 A simple clone may look like this (with no 'have' lines):

diff --git a/fetch-pack.c b/fetch-pack.c
index f12bfcdbb12c0bde9271ba45e5d8b6941439efc1..986b1efebca1853ff98ce71153dfd546d8778a23 100644 (file)
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -240,6 +240,8 @@ static enum ack_type get_ack(int fd, unsigned char *result_sha1)
                        return ACK;
                }
        }
+       if (skip_prefix(line, "ERR ", &arg))
+               die(_("remote error: %s"), arg);
        die(_("git fetch-pack: expected ACK/NAK, got '%s'"), line);
 }