ssh kitten: Send data without a roundtrip

Send data to the remote side without waiting for a data request. Avoids
an extra roundtrip during initialization.

shell-integration/ssh/askpass.py

@@ -27,6 +27,7 @@ with SharedMemory(
     shm.flush()
     with open(os.ctermid(), 'wb') as f:
         f.write(f'\x1bP@kitty-ask|{shm.name}\x1b\\'.encode('ascii'))
+        f.flush()
     while True:
         # TODO: Replace sleep() with a mutex and condition variable created in the shared memory
         time.sleep(0.05)

shell-integration/ssh/bootstrap.sh

@@ -73,8 +73,7 @@ login_cwd=""
 
 request_data="REQUEST_DATA"
 trap "cleanup_on_bootstrap_exit" EXIT
-dcs_to_kitty "ssh" "id="REQUEST_ID":pwfile="PASSWORD_FILENAME":pw="DATA_PASSWORD""
-record_separator=$(printf "\036")
+[ "$request_data" = "1" ] && dcs_to_kitty "ssh" "id="REQUEST_ID":pwfile="PASSWORD_FILENAME":pw="DATA_PASSWORD""
 
 mv_files_and_dirs() {
     cwd="$PWD"
@@ -135,16 +134,6 @@ untar_and_read_env() {
     tdir=""
 }
 
-read_record() {
-    record=""
-    while :; do
-        read_one_byte_from_tty || die "Reading a byte from the TTY failed"
-        [ "$n" = "$record_separator" ] && break
-        record="$record$n"
-    done
-    printf "%s" "$record"
-}
-
 get_data() {
     started="n"
     while IFS= read -r line; do