invoke git.exe instead of git in /mnt

See: microsoft/WSL#4197

templates/.shrc

@@ -1,16 +1,20 @@
 _PS1() {
-	local e=${1:-$?} cwd branch stage context
+	local e=${1:-$?} git=git cwd branch stage context
 
 	case $e in
 		0) cwd='\[\033[38;5;2m\]\w\[\033[m\]' ;;
 		*) cwd='\[\033[38;5;1m\]\w\[\033[m\]' ;;
 	esac
 
-	branch=$(git rev-parse --abbrev-ref HEAD 2> /dev/null)
+	case $PWD in
+		/mnt/*) git=git.exe ;;
+	esac
+
+	branch=$($git rev-parse --abbrev-ref HEAD 2> /dev/null)
 
 	if test -n "$branch"; then
-		git status --porcelain 2> /dev/null | grep -q '^\w' && stage=1
-		git status --porcelain 2> /dev/null | grep -qv '^\w' && stage=$((stage + 2))
+		$git status --porcelain 2> /dev/null | grep -q '^\w' && stage=1
+		$git status --porcelain 2> /dev/null | grep -qv '^\w' && stage=$((stage + 2))
 
 		case $stage in
 			1) stage='\[\033[38;5;12m\]*\[\033[m\]' ;;