checkout: Provide useful error with checkout -H and incompat mode

Previously we'd assert and dump core if one used `checkout -H` without
`-U` on a bare-user repo, because we'd hit the bare-user symlink case.

Rework the code to handle this, and add tests. I hit this when I was going to
suggest to someone to use `-H` to ensure they were getting hardlinks.

Closes: #779
Approved by: jlebon

tests/basic-test.sh

@@ -38,9 +38,45 @@ if grep bare-user-only repo/config; then
     CHECKOUT_U_ARG="-U"
 fi
 
+validate_checkout_basic() {
+    (cd $1;
+     assert_has_file firstfile
+     assert_has_file baz/cow
+     assert_file_has_content baz/cow moo
+     assert_has_file baz/deeper/ohyeah
+     )
+}
+
 $OSTREE checkout test2 checkout-test2
+validate_checkout_basic checkout-test2
 echo "ok checkout"
 
+# Note this tests bare-user *and* bare-user-only
+rm checkout-test2 -rf
+if grep bare-user repo/config; then
+    $OSTREE checkout -U -H test2 checkout-test2
+else
+    $OSTREE checkout -H test2 checkout-test2
+fi
+validate_checkout_basic checkout-test2
+rm checkout-test2 -rf
+# Only do these tests on bare-user/bare, not bare-user-only
+# since the latter automatically synthesizes -U if it's not passed.
+if ! grep -q bare-user-only repo/config; then
+if grep -q bare-user repo/config; then
+    if $OSTREE checkout -H test2 checkout-test2 2>err.txt; then
+        assert_not_reached "checkout -H worked?"
+    fi
+    assert_file_has_content err.txt "User repository.*requires.*user"
+else
+    if $OSTREE checkout -U -H test2 checkout-test2 2>err.txt; then
+        assert_not_reached "checkout -H worked?"
+    fi
+    assert_file_has_content err.txt "Bare repository mode cannot hardlink in user"
+fi
+fi
+echo "ok checkout -H"
+
 $OSTREE rev-parse test2
 $OSTREE rev-parse 'test2^'
 $OSTREE rev-parse 'test2^^' 2>/dev/null && fatal "rev-parse test2^^ unexpectedly succeeded!"
@@ -64,13 +100,9 @@ ostree_repo_init test-repo --mode=bare-user
 rm test-repo -rf
 echo "ok repo-init on existing repo"
 
+rm checkout-test2 -rf
+$OSTREE checkout test2 checkout-test2
 cd checkout-test2
-assert_has_file firstfile
-assert_has_file baz/cow
-assert_file_has_content baz/cow moo
-assert_has_file baz/deeper/ohyeah
-echo "ok content"
-
 rm firstfile
 $OSTREE commit ${COMMIT_ARGS} -b test2 -s delete