tests/testlib/wait-on-file

interfaces: introduce and use a protocol class for the `mpatch` module

See f2832de2a46c for details when this was done for the `bdiff` module.

Two things worth pointing out-

  1) The `cffi` module "inherits" the `pure` implementation of `patchedsize()`
     because of its wildcard import.
  2) It's odd that the `mpatchError` lives in both `pure` and `cext` modules.

I initially thought to move the exception into the new class, and make the
existing class name an alias to the class in the new location, but the exception
is created in C code by the `cext` module, so that won't work.  I don't think a
protocol class is approriate, because there's nothing special about the class to
distinguish from any other `Exception`.  Fortunately, nobody is catching this
exception in core, so we can kick the can down the road.

#!/bin/sh
#
# wait up to TIMEOUT seconds until a WAIT_ON_FILE is created.
#
# In addition, this script can create CREATE_FILE once it is ready to wait.

if [ $# -lt 2 ] || [ $# -gt 3 ]; then
    echo $#
    echo "USAGE: $0 TIMEOUT WAIT_ON_FILE [CREATE_FILE]"
fi

timer="$1"

# If the test timeout have been extended, also scale the timer relative
# to the normal timing.
if [ "$HGTEST_TIMEOUT_DEFAULT" -lt "$HGTEST_TIMEOUT" ]; then
    timer=$(( ( $timer * $HGTEST_TIMEOUT) / $HGTEST_TIMEOUT_DEFAULT ))
fi

max_time=$timer

# Scale the timeout to match the sleep steps below, i.e. 1/0.02.
timer=$(( 50 * $timer ))

wait_on="$2"
create=""
if [ $# -eq 3 ]; then
    create="$3"
fi

if [ -n "$create" ]; then
    touch "$create"
    create=""
fi
while [ "$timer" -gt 0 ] && !([ -e "$wait_on" ] || [ -L "$wait_on" ]) ; do
    timer=$(( $timer - 1))
    sleep 0.02
done
if [ "$timer" -le 0 ]; then
    echo "file not created after $max_time seconds: $wait_on" >&2
    exit 1
fi