v symlink: use a .symlink/v.bat launcher to avoid global PATH polution

.gitignore

@@ -66,3 +66,4 @@ cachegrind.out.*
 .DS_Store
 ._*
 thumbs.db
+/.symlink/*

cmd/tools/vsymlink.v

@@ -2,17 +2,15 @@ import os
 import v.pref
 
 fn main(){
-	vexe := pref.vexe_path()
 	$if windows {
-		vdir := os.real_path(os.dir(vexe))
+		setup_symlink_on_windows()
-		res := os.system('setx /M PATH "$vdir;%PATH%"')
+	} $else {
-		if res == 0 {
+		setup_symlink_on_unix()
-			println('v has been prepended to the path')
-			exit(0)
 	}
-		exit(1)
+}
-	}
+
-	//
+fn setup_symlink_on_unix(){
+	vexe := pref.vexe_path()
 	mut link_path := '/usr/local/bin/v'
 	mut ret := os.exec('ln -sf $vexe $link_path') or {
 		panic(err)
@@ -34,3 +32,58 @@ fn main(){
 		println('Failed to create symlink "$link_path". Try again with sudo.')
 	}
 }
+
+fn setup_symlink_on_windows(){
+	vexe := pref.vexe_path()
+	// NB: Putting $vdir directly into PATH will also result in
+	// make.bat being global, which is NOT what we want.
+	//
+	// Instead, we create a small launcher v.bat, in a new local
+	// folder .symlink/ . That .symlink/ folder can then be put
+	// in PATH without poluting it with anything else - just a
+	// `v` command will be available, simillar to unix.
+	//
+	// Creating a real NTFS symlink to the real executable was also
+	// tried, but then os.real_path( os.executable() ) returns the
+	// path to the symlink, unfortunately, unlike on posix systems
+	// ¯\_(ツ)_/¯
+	vdir := os.real_path(os.dir(vexe))
+	vsymlinkdir := os.join_path(vdir, '.symlink')
+	vsymlinkbat := os.join_path(vsymlinkdir, 'v.bat')
+	os.rmdir_all(vsymlinkdir)
+	os.mkdir_all(vsymlinkdir)
+	os.write_file(vsymlinkbat, '$vexe %*')
+	if !os.exists( vsymlinkbat ) {
+		eprintln('Could not create $vsymlinkbat')
+		exit(1)
+	}
+	println('Created $vsymlinkbat .')
+	current_paths := os.getenv('PATH').split(';').map(it.trim('/\\'))
+	if vsymlinkdir in current_paths {
+		println('$vsymlinkdir is already on your PATH')
+		println('Try running `v version`')
+		exit(0)
+	}
+	// put vsymlinkdir first, prevent duplicates:
+	mut new_paths := [ vsymlinkdir ]
+	for p in current_paths {
+		if p !in new_paths {
+			new_paths << p
+		}
+	}
+	//
+	change_path_cmd := 'setx /M PATH "' + new_paths.join(';') +'"'
+	println('Changing global PATH with:')
+	println(change_path_cmd)
+	res := os.system(change_path_cmd)
+	if res == 0 {
+		println('')
+		println('$vsymlinkdir has been prepended to PATH.')
+		println('Try running `v version`.')
+		exit(0)
+	} else {
+		println('Could not run `setx`, probably you are not an administrator.')
+		println('`v symlink` should be launched with admin privileges.')
+		exit(1)
+	}
+}