Fix input git to correctly handle subdir argument (solve #884)

Previously, the subdir argument wa ignored by dagger input git.
I've fix that behavior and add a test.

Signed-off-by: Tom Chauveau <tom.chauveau@epitech.eu>

tests/cli/input/git/main.cue

@@ -0,0 +1,18 @@
+package testing
+
+import (
+	"alpha.dagger.io/dagger"
+	"alpha.dagger.io/os"
+)
+
+// Input https://github.com/dagger/examples/tree/main/todoapp
+TestRepo: dagger.#Input & {dagger.#Artifact}
+
+// Check README.md
+TestFolder: os.#Container & {
+	always: true
+	command: #"""
+			grep -q "Todo APP" /input/repo/README.md
+		"""#
+	mount: "/input/repo": from: TestRepo
+}