upload-pack: optionally allow fetching any sha1dt/smart-http-detect-server-going-away

It seems a little silly to do a reachabilty check in the case where we
trust the user to access absolutely everything in the repository.

Also, it's racy in a distributed system -- perhaps one server
advertises a ref, but another has since had a force-push to that ref,
and perhaps the two HTTP requests end up directed to these different
servers.

Signed-off-by: David Turner <dturner@twosigma.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 39 insertions, 4 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index a0ab66aae7..b7f9991cc7 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -2961,6 +2961,11 @@ uploadpack.allowReachableSHA1InWant::
 	calculating object reachability is computationally expensive.
 	Defaults to `false`.
 
+uploadpack.allowAnySHA1InWant::
+	Allow `upload-pack` to accept a fetch request that asks for any
+	object at all.
+	Defaults to `false`.
+
 uploadpack.keepAlive::
 	When `upload-pack` has started `pack-objects`, there may be a
 	quiet period while `pack-objects` prepares the pack. Normally
diff --git a/Documentation/git-fetch-pack.txt b/Documentation/git-fetch-pack.txt
index d45f6adc69..f7ebe36a7b 100644
--- a/Documentation/git-fetch-pack.txt
+++ b/Documentation/git-fetch-pack.txt
@@ -119,9 +119,9 @@ be in a separate packet, and the list must end with a flush packet.
 	$GIT_DIR (e.g. "HEAD", "refs/heads/master").  When
 	unspecified, update from all heads the remote side has.
 +
-If the remote has enabled the options `uploadpack.allowTipSHA1InWant` or
-`uploadpack.allowReachableSHA1InWant`, they may alternatively be 40-hex
-sha1s present on the remote.
+If the remote has enabled the options `uploadpack.allowTipSHA1InWant`,
+`uploadpack.allowReachableSHA1InWant`, or `uploadpack.allowAnySHA1InWant`,
+they may alternatively be 40-hex sha1s present on the remote.
 
 SEE ALSO
 --------
diff --git a/t/t5551-http-fetch-smart.sh b/t/t5551-http-fetch-smart.sh
index 43665ab4a8..8d3db405c0 100755
--- a/t/t5551-http-fetch-smart.sh
+++ b/t/t5551-http-fetch-smart.sh
@@ -306,6 +306,28 @@ test_expect_success 'test allowreachablesha1inwant with unreachable' '
 	test_must_fail git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
 '
 
+test_expect_success 'test allowanysha1inwant with unreachable' '
+	test_when_finished "rm -rf test_reachable.git; git reset --hard $(git rev-parse HEAD)" &&
+
+	#create unreachable sha
+	echo content >file2 &&
+	git add file2 &&
+	git commit -m two &&
+	git push public HEAD:refs/heads/doomed &&
+	git push public :refs/heads/doomed &&
+
+	server="$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
+	master_sha=$(git -C "$server" rev-parse refs/heads/master) &&
+	git -C "$server" config uploadpack.allowreachablesha1inwant 1 &&
+
+	git init --bare test_reachable.git &&
+	git -C test_reachable.git remote add origin "$HTTPD_URL/smart/repo.git" &&
+	test_must_fail git -C test_reachable.git fetch origin "$(git rev-parse HEAD)" &&
+
+	git -C "$server" config uploadpack.allowanysha1inwant 1 &&
+	git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
+'
+
 test_expect_success EXPENSIVE 'http can handle enormous ref negotiation' '
 	(
 		cd "$HTTPD_DOCUMENT_ROOT_PATH/repo.git" &&
diff --git a/upload-pack.c b/upload-pack.c
index e0db8b42be..7597ba3405 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -46,6 +46,8 @@ static int no_progress, daemon_mode;
 #define ALLOW_TIP_SHA1	01
 /* Allow request of a sha1 if it is reachable from a ref (possibly hidden ref). */
 #define ALLOW_REACHABLE_SHA1	02
+/* Allow request of any sha1. Implies ALLOW_TIP_SHA1 and ALLOW_REACHABLE_SHA1. */
+#define ALLOW_ANY_SHA1	07
 static unsigned int allow_unadvertised_object_request;
 static int shallow_nr;
 static struct object_array have_obj;
@@ -825,7 +827,8 @@ static void receive_needs(void)
 			    sha1_to_hex(sha1_buf));
 		if (!(o->flags & WANTED)) {
 			o->flags |= WANTED;
-			if (!is_our_ref(o))
+			if (!((allow_unadvertised_object_request & ALLOW_ANY_SHA1) == ALLOW_ANY_SHA1
+			      || is_our_ref(o)))
 				has_non_tip = 1;
 			add_object_array(o, NULL, &want_obj);
 		}
@@ -1008,6 +1011,11 @@ static int upload_pack_config(const char *var, const char *value, void *unused)
 			allow_unadvertised_object_request |= ALLOW_REACHABLE_SHA1;
 		else
 			allow_unadvertised_object_request &= ~ALLOW_REACHABLE_SHA1;
+	} else if (!strcmp("uploadpack.allowanysha1inwant", var)) {
+		if (git_config_bool(var, value))
+			allow_unadvertised_object_request |= ALLOW_ANY_SHA1;
+		else
+			allow_unadvertised_object_request &= ~ALLOW_ANY_SHA1;
 	} else if (!strcmp("uploadpack.keepalive", var)) {
 		keepalive = git_config_int(var, value);
 		if (!keepalive)