connect: advertized capability is not a ref

When cloning an empty repository served by standard git, "git clone" produces
the following reassuring message:

$ git clone git://localhost/tmp/empty
Cloning into 'empty'...
warning: You appear to have cloned an empty repository.
Checking connectivity... done.

Meanwhile when cloning an empty repository served by JGit, the output is more
haphazard:

$ git clone git://localhost/tmp/empty
Cloning into 'empty'...
Checking connectivity... done.
warning: remote HEAD refers to nonexistent ref, unable to checkout.

This is a common command to run immediately after creating a remote repository
as preparation for adding content to populate it and pushing. The warning is
confusing and needlessly worrying.

The cause is that, since v3.1.0.201309270735-rc1~22 (Advertise capabilities
with no refs in upload service., 2013-08-08), JGit's ref advertisement includes
a ref named capabilities^{} to advertise its capabilities on, while git's ref
advertisement is empty in this case. This allows the client to learn about the
server's capabilities and is needed, for example, for fetch-by-sha1 to work
when no refs are advertised.

This also affects "ls-remote". For example, against an empty repository served
by JGit:

$ git ls-remote git://localhost/tmp/empty
0000000000000000000000000000000000000000        capabilities^{}

Git advertises the same capabilities^{} ref in its ref advertisement for push
but since it never did so for fetch, the client didn't need to handle this
case.  Handle it.

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

diff --git a/connect.c b/connect.c
index 067cf409a8360b374f587d47aa87fa7d44b7614a..5ccbd1041eff714055e8bf07ca5016a1b8d0302a 100644 (file)
--- a/connect.c
+++ b/connect.c
@@ -123,6 +123,7 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
         * response does not necessarily mean an ACL problem, though.
         */
        int saw_response;
+       int got_dummy_ref_with_capabilities_declaration = 0;
 
        *list = NULL;
        for (saw_response = 0; ; saw_response = 1) {
@@ -172,8 +173,21 @@ struct ref **get_remote_heads(int in, char *src_buf, size_t src_len,
                        continue;
                }
 
+               if (!strcmp(name, "capabilities^{}")) {
+                       if (saw_response)
+                               die("protocol error: unexpected capabilities^{}");
+                       if (got_dummy_ref_with_capabilities_declaration)
+                               die("protocol error: multiple capabilities^{}");
+                       got_dummy_ref_with_capabilities_declaration = 1;
+                       continue;
+               }
+
                if (!check_ref(name, flags))
                        continue;
+
+               if (got_dummy_ref_with_capabilities_declaration)
+                       die("protocol error: unexpected ref after capabilities^{}");
+
                ref = alloc_ref(buffer + GIT_SHA1_HEXSZ + 1);
                oidcpy(&ref->old_oid, &old_oid);
                *list = ref;

diff --git a/t/t5512-ls-remote.sh b/t/t5512-ls-remote.sh
index 819b9ddd0f917a21e3edf7122f99cfb04f4b7a8f..befdfeefc603e42ad1ce69599fd1b1142917a8d7 100755 (executable)
--- a/t/t5512-ls-remote.sh
+++ b/t/t5512-ls-remote.sh
@@ -207,5 +207,45 @@ test_expect_success 'ls-remote --symref omits filtered-out matches' '
        test_cmp expect actual
 '
 
+test_lazy_prereq GIT_DAEMON '
+       test_tristate GIT_TEST_GIT_DAEMON &&
+       test "$GIT_TEST_GIT_DAEMON" != false
+'
+
+# This test spawns a daemon, so run it only if the user would be OK with
+# testing with git-daemon.
+test_expect_success PIPE,JGIT,GIT_DAEMON 'indicate no refs in standards-compliant empty remote' '
+       JGIT_DAEMON_PORT=${JGIT_DAEMON_PORT-${this_test#t}} &&
+       JGIT_DAEMON_PID= &&
+       git init --bare empty.git &&
+       >empty.git/git-daemon-export-ok &&
+       mkfifo jgit_daemon_output &&
+       {
+               jgit daemon --port="$JGIT_DAEMON_PORT" . >jgit_daemon_output &
+               JGIT_DAEMON_PID=$!
+       } &&
+       test_when_finished kill "$JGIT_DAEMON_PID" &&
+       {
+               read line &&
+               case $line in
+               Exporting*)
+                       ;;
+               *)
+                       echo "Expected: Exporting" &&
+                       false;;
+               esac &&
+               read line &&
+               case $line in
+               "Listening on"*)
+                       ;;
+               *)
+                       echo "Expected: Listening on" &&
+                       false;;
+               esac
+       } <jgit_daemon_output &&
+       # --exit-code asks the command to exit with 2 when no
+       # matching refs are found.
+       test_expect_code 2 git ls-remote --exit-code git://localhost:$JGIT_DAEMON_PORT/empty.git
+'
 
 test_done