Make gotd work around an error shown by 'git push' with no changes to send.
 
git push would show output like:
 = [up to date]      main -> main
 error: failed to push some refs to 'ssh://example.com/git/repo.git
 
This happened because "unexpected end of file" and "unexpected flush packet"
errors were reported to the client via gotsh.

diff cf31b4749a965b44fa03a3c98bdfc8b60f2c987d 68f4e4ff48e662914972bd5d822eccd8aa161a03
commit - cf31b4749a965b44fa03a3c98bdfc8b60f2c987d
commit + 68f4e4ff48e662914972bd5d822eccd8aa161a03
blob - 8f00f2699c2d87d84a815df4188c27ed9fcc45c0
blob + e4c9601581a5f7e5f5944692c0f36c0130bacfdd
--- gotd/session.c
+++ gotd/session.c
@@ -1046,6 +1046,17 @@ session_dispatch_client(int fd, short events, void *ar
 		if (err) {
 			if (err->code == GOT_ERR_PRIVSEP_READ)
 				err = NULL;
+			else if (err->code == GOT_ERR_EOF &&
+			    client->state == GOTD_STATE_EXPECT_CAPABILITIES) {
+				/*
+				 * The client has closed its socket before
+				 * sending its capability announcement.
+				 * This can happen when Git clients have
+				 * no ref-updates to send.
+				 */
+				disconnect_on_error(client, err);
+				return;
+			}
 			break;
 		}
 
blob - 3d1c9a901f008fc32a17f1ab6a9abc5b444cf986
blob + b811009e08d9088194ccc086a17fcecac0da7fde
--- lib/serve.c
+++ lib/serve.c
@@ -1270,7 +1270,10 @@ serve_write(int infd, int outfd, int gotd_sock, const 
 		if (err)
 			goto done;
 		if (n == 0) {
-			if (curstate != STATE_EXPECT_MORE_REF_UPDATES) {
+			if (curstate == STATE_EXPECT_REF_UPDATE) {
+				/* The client will not send us anything. */
+				goto done;
+			} else if (curstate != STATE_EXPECT_MORE_REF_UPDATES) {
 				err = got_error_msg(GOT_ERR_BAD_PACKET,
 				    "unexpected flush packet received");
 				goto done;
blob - daff924b47ca360160665215790f700bf0f8bfda
blob + 83927b35c3c889b14f84b418b4d7235c156e0444
--- regress/gotd/repo_write.sh
+++ regress/gotd/repo_write.sh
@@ -112,6 +112,16 @@ EOF
 		return 1
 	fi
 
+	# Verify that git push reports no changes to send and no error.
+	(cd $testroot/repo-clone3 && git push -q > $testroot/stdout \
+		2> $testroot/stderr)
+	ret=$?
+	if [ $ret -ne 0 ]; then
+		echo "git pull failed unexpectedly" >&2
+		test_done "$testroot" "1"
+		return 1
+	fi
+
 	# sending to a repository should result in a new pack file
 	ls -R ${GOTD_TEST_REPO}/objects/pack > $testroot/repo-list.after
 	diff -u $testroot/repo-list.before $testroot/repo-list.after \