tests/nixos/fetch-git: Add http-auth test

tests/nixos/fetch-git/test-cases/http-auth/default.nix

@@ -0,0 +1,40 @@
+{ config, ... }:
+{
+  description = "can fetch a private git repo via http";
+  repo.private = true;
+  script = ''
+    # add a file to the repo
+    client.succeed(f"""
+      echo ${config.name /* to make the git tree and store path unique */} > {repo.path}/test-case \
+      && echo lutyabrook > {repo.path}/new-york-state \
+      && {repo.git} add test-case new-york-state \
+      && {repo.git} commit -m 'commit1'
+    """)
+
+    # memoize the revision
+    rev1 = client.succeed(f"""
+      {repo.git} rev-parse HEAD
+    """).strip()
+
+    # push to the server
+    client.succeed(f"""
+      {repo.git} push origin main
+    """)
+
+    # fetch the repo via nix
+    fetched1 = client.succeed(f"""
+      nix eval --impure --raw --expr "(builtins.fetchGit {repo.remote}).outPath"
+    """)
+
+    # check if the committed file is there
+    client.succeed(f"""
+      test -f {fetched1}/new-york-state
+    """)
+
+    # check if the revision is the same
+    rev1_fetched = client.succeed(f"""
+      nix eval --impure --raw --expr "(builtins.fetchGit {repo.remote}).rev"
+    """).strip()
+    assert rev1 == rev1_fetched, f"rev1: {rev1} != rev1_fetched: {rev1_fetched}"
+  '';
+}