For now, only one `pyodide` can be loaded in a given global scope because we need to use a global variable for package loading. This changes `loadPyodide` so that it no longer defines `globalThis.pyodide` in favor of just returning `pyodide` from `loadPyodide`. `Module` is placed on the global object as `globalThis.__pyodide_module` for the purposes of package loading. I added documentation to explicitly state that `loadPyodide` can only be run once in each global Javascript context, an error will be thrown otherwise.

This has two advantages: 
1. The returned `pyodide` module is understandable to Typescript and other code analysis, whereas the global variable is not understandable.
2. If in the future we are able to remove the global variable, no further API change will be needed (other than relaxing the documented "pyodide must be globally-unique" constraint). I figure it's better to make this API change earlier rather than later.

It will be possible to completely remove the global variable dependence when Firefox implements support for using ES6 modules in webworkers (see https://bugzilla.mozilla.org/show_bug.cgi?id=1247687).
API Don't expose pyodide as a global variable in loadPyodide. For now, only one `pyodide` can be loaded in a given global scope because we need to use a global variable for package loading. This changes `loadPyodide` so that it no longer defines `globalThis.pyodide` in favor of just returning `pyodide` from `loadPyodide`. `Module` is placed on the global object as `globalThis.__pyodide_module` for the purposes of package loading. I added documentation to explicitly state that `loadPyodide` can only be run once in each global Javascript context, an error will be thrown otherwise.

This has two advantages: 
1. The returned `pyodide` module is understandable to Typescript and other code analysis, whereas the global variable is not understandable.
2. If in the future we are able to remove the global variable, no further API change will be needed (other than relaxing the documented "pyodide must be globally-unique" constraint). I figure it's better to make this API change earlier rather than later.

It will be possible to completely remove the global variable dependence when Firefox implements support for using ES6 modules in webworkers (see https://bugzilla.mozilla.org/show_bug.cgi?id=1247687).
#!/usr/bin/perl

use strict;
use warnings;
use IPC::Open2;

# An example hook script to integrate Watchman
# (https://facebook.github.io/watchman/) with git to speed up detecting
# new and modified files.
#
# The hook is passed a version (currently 1) and a time in nanoseconds
# formatted as a string and outputs to stdout all files that have been
# modified since the given time. Paths must be relative to the root of
# the working tree and separated by a single NUL.
#
# To enable this hook, rename this file to "query-watchman" and set
# 'git config core.fsmonitor .git/hooks/query-watchman'
#
my ($version, $time) = @ARGV;

# Check the hook interface version

if ($version == 1) {
	# convert nanoseconds to seconds
	# subtract one second to make sure watchman will return all changes
	$time = int ($time / 1000000000) - 1;
} else {
	die "Unsupported query-fsmonitor hook version '$version'.\n" .
	    "Falling back to scanning...\n";
}

my $git_work_tree;
if ($^O =~ 'msys' || $^O =~ 'cygwin') {
	$git_work_tree = Win32::GetCwd();
	$git_work_tree =~ tr/\\/\//;
} else {
	require Cwd;
	$git_work_tree = Cwd::cwd();
}

my $retry = 1;

launch_watchman();

sub launch_watchman {

	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
	    or die "open2() failed: $!\n" .
	    "Falling back to scanning...\n";

	# In the query expression below we're asking for names of files that
	# changed since $time but were not transient (ie created after
	# $time but no longer exist).
	#
	# To accomplish this, we're using the "since" generator to use the
	# recency index to select candidate nodes and "fields" to limit the
	# output to file names only.

	my $query = <<"	END";
		["query", "$git_work_tree", {
			"since": $time,
			"fields": ["name"]
		}]
	END

	print CHLD_IN $query;
	close CHLD_IN;
	my $response = do {local $/; <CHLD_OUT>};

	die "Watchman: command returned no output.\n" .
	    "Falling back to scanning...\n" if $response eq "";
	die "Watchman: command returned invalid output: $response\n" .
	    "Falling back to scanning...\n" unless $response =~ /^\{/;

	my $json_pkg;
	eval {
		require JSON::XS;
		$json_pkg = "JSON::XS";
		1;
	} or do {
		require JSON::PP;
		$json_pkg = "JSON::PP";
	};

	my $o = $json_pkg->new->utf8->decode($response);

	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
		print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
		$retry--;
		qx/watchman watch "$git_work_tree"/;
		die "Failed to make watchman watch '$git_work_tree'.\n" .
		    "Falling back to scanning...\n" if $? != 0;

		# Watchman will always return all files on the first query so
		# return the fast "everything is dirty" flag to git and do the
		# Watchman query just to get it over with now so we won't pay
		# the cost in git to look up each individual file.
		print "/\0";
		eval { launch_watchman() };
		exit 0;
	}

	die "Watchman: $o->{error}.\n" .
	    "Falling back to scanning...\n" if $o->{error};

	binmode STDOUT, ":utf8";
	local $, = "\0";
	print @{$o->{files}};
}

#!/usr/bin/perl

use strict;
use warnings;
use IPC::Open2;

# An example hook script to integrate Watchman
# (https://facebook.github.io/watchman/) with git to speed up detecting
# new and modified files.
#
# The hook is passed a version (currently 1) and a time in nanoseconds
# formatted as a string and outputs to stdout all files that have been
# modified since the given time. Paths must be relative to the root of
# the working tree and separated by a single NUL.
#
# To enable this hook, rename this file to "query-watchman" and set
# 'git config core.fsmonitor .git/hooks/query-watchman'
#
my ($version, $time) = @ARGV;

# Check the hook interface version

if ($version == 1) {
	# convert nanoseconds to seconds
	# subtract one second to make sure watchman will return all changes
	$time = int ($time / 1000000000) - 1;
} else {
	die "Unsupported query-fsmonitor hook version '$version'.\n" .
	    "Falling back to scanning...\n";
}

my $git_work_tree;
if ($^O =~ 'msys' || $^O =~ 'cygwin') {
	$git_work_tree = Win32::GetCwd();
	$git_work_tree =~ tr/\\/\//;
} else {
	require Cwd;
	$git_work_tree = Cwd::cwd();
}

my $retry = 1;

launch_watchman();

sub launch_watchman {

	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
	    or die "open2() failed: $!\n" .
	    "Falling back to scanning...\n";

	# In the query expression below we're asking for names of files that
	# changed since $time but were not transient (ie created after
	# $time but no longer exist).
	#
	# To accomplish this, we're using the "since" generator to use the
	# recency index to select candidate nodes and "fields" to limit the
	# output to file names only.

	my $query = <<"	END";
		["query", "$git_work_tree", {
			"since": $time,
			"fields": ["name"]
		}]
	END

	print CHLD_IN $query;
	close CHLD_IN;
	my $response = do {local $/; <CHLD_OUT>};

	die "Watchman: command returned no output.\n" .
	    "Falling back to scanning...\n" if $response eq "";
	die "Watchman: command returned invalid output: $response\n" .
	    "Falling back to scanning...\n" unless $response =~ /^\{/;

	my $json_pkg;
	eval {
		require JSON::XS;
		$json_pkg = "JSON::XS";
		1;
	} or do {
		require JSON::PP;
		$json_pkg = "JSON::PP";
	};

	my $o = $json_pkg->new->utf8->decode($response);

	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
		print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
		$retry--;
		qx/watchman watch "$git_work_tree"/;
		die "Failed to make watchman watch '$git_work_tree'.\n" .
		    "Falling back to scanning...\n" if $? != 0;

		# Watchman will always return all files on the first query so
		# return the fast "everything is dirty" flag to git and do the
		# Watchman query just to get it over with now so we won't pay
		# the cost in git to look up each individual file.
		print "/\0";
		eval { launch_watchman() };
		exit 0;
	}

	die "Watchman: $o->{error}.\n" .
	    "Falling back to scanning...\n" if $o->{error};

	binmode STDOUT, ":utf8";
	local $, = "\0";
	print @{$o->{files}};
}
