Normalize path names for maintainer scripts in Git repositories

Previously if the PKGBUILD specified something like './postinst' for say, the 'postinst' script, the update script wouldn't be able to find the file. Now we normalize path names so prefixes like './' are removed.

aurweb/git/update.py

@@ -399,7 +399,7 @@ def main():  # noqa: C901
                 )
                 script = srcinfo.get_variable(script_name)[0]
 
-                if script not in commit.tree:
+                if os.path.normpath(script) not in commit.tree:
                     die_commit(f"Missing {script_name} file {script}.", str(commit.id))
 
         # Check sources.

test/test_git.py

@@ -144,10 +144,13 @@ def test_basic_push():
             f"source_amd64 = {source_url_prefix}/source6",
             f"focal_source_amd64 = {source_url_prefix}/source7",
             f"focal_source_amd64 = {source_url_prefix}/source8",
+            "postinst = ./testfile",
         ],
     )
 
-    repo.add(["PKGBUILD", ".SRCINFO"])
+    write_file("testfile", [])
+
+    repo.add(["PKGBUILD", ".SRCINFO", "testfile"])
     repo.commit()
     repo.push()