fsmonitor: simplify determining the git worktree under Windows

Simplify and speed up the process of finding the git worktree when
running on Windows by keeping it in perl and avoiding spawning helper
processes.

Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7519/fsmonitor-watchman

@@ -29,17 +29,10 @@ if ($version == 1) {
 	    "Falling back to scanning...\n";
 }
 
-# Convert unix style paths to escaped Windows style paths when running
-# in Windows command prompt
-
-my $system = `uname -s`;
-$system =~ s/[\r\n]+//g;
 my $git_work_tree;
-
-if ($system =~ m/^MSYS_NT/ || $system =~ m/^MINGW/) {
-	$git_work_tree = `cygpath -aw "\$PWD"`;
-	$git_work_tree =~ s/[\r\n]+//g;
-	$git_work_tree =~ s,\\,/,g;
+if ($^O =~ 'msys' || $^O =~ 'cygwin') {
+	$git_work_tree = Win32::GetCwd();
+	$git_work_tree =~ tr/\\/\//;
 } else {
 	require Cwd;
 	$git_work_tree = Cwd::cwd();

templates/hooks--fsmonitor-watchman.sample

@@ -28,17 +28,10 @@ if ($version == 1) {
 	    "Falling back to scanning...\n";
 }
 
-# Convert unix style paths to escaped Windows style paths when running
-# in Windows command prompt
-
-my $system = `uname -s`;
-$system =~ s/[\r\n]+//g;
 my $git_work_tree;
-
-if ($system =~ m/^MSYS_NT/ || $system =~ m/^MINGW/) {
-	$git_work_tree = `cygpath -aw "\$PWD"`;
-	$git_work_tree =~ s/[\r\n]+//g;
-	$git_work_tree =~ s,\\,/,g;
+if ($^O =~ 'msys' || $^O =~ 'cygwin') {
+	$git_work_tree = Win32::GetCwd();
+	$git_work_tree =~ tr/\\/\//;
 } else {
 	require Cwd;
 	$git_work_tree = Cwd::cwd();