unwritable tests: assert exact error output

In preparation for fixing a regression where we started emitting some
of these error messages twice, let's assert what the output from "git
commit" and friends is now in the case of permission errors.

As noted in [1] using test_expect_failure to mark up a TODO test has
some unexpected edge cases, e.g. we don't want to break --run=3 by
skipping the "test_lazy_prereq" here. This pattern allows us to test
just the test_cmp (and the "cat", which shouldn't fail) with the added
"test_expect_failure", we'll flip that to a "test_expect_success" in
the next commit.

1. https://lore.kernel.org/git/[email protected]/T/#u

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

t/t0004-unwritable.sh

@@ -18,27 +18,66 @@ test_expect_success setup '
 test_expect_success POSIXPERM,SANITY 'write-tree should notice unwritable repository' '
 	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
 	chmod a-w .git/objects .git/objects/?? &&
-	test_must_fail git write-tree
+	test_must_fail git write-tree 2>out.write-tree
+'
+
+test_lazy_prereq WRITE_TREE_OUT 'test -e "$TRASH_DIRECTORY"/out.write-tree'
+test_expect_success WRITE_TREE_OUT 'write-tree output on unwritable repository' '
+	cat >expect <<-\EOF &&
+	error: insufficient permission for adding an object to repository database .git/objects
+	fatal: git-write-tree: error building trees
+	EOF
+	test_cmp expect out.write-tree
 '
 
 test_expect_success POSIXPERM,SANITY 'commit should notice unwritable repository' '
 	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
 	chmod a-w .git/objects .git/objects/?? &&
-	test_must_fail git commit -m second
+	test_must_fail git commit -m second 2>out.commit
+'
+
+test_lazy_prereq COMMIT_OUT 'test -e "$TRASH_DIRECTORY"/out.commit'
+test_expect_failure COMMIT_OUT 'commit output on unwritable repository' '
+	cat >expect <<-\EOF &&
+	error: insufficient permission for adding an object to repository database .git/objects
+	error: Error building trees
+	EOF
+	test_cmp expect out.commit
 '
 
 test_expect_success POSIXPERM,SANITY 'update-index should notice unwritable repository' '
 	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
 	echo 6O >file &&
 	chmod a-w .git/objects .git/objects/?? &&
-	test_must_fail git update-index file
+	test_must_fail git update-index file 2>out.update-index
+'
+
+test_lazy_prereq UPDATE_INDEX_OUT 'test -e "$TRASH_DIRECTORY"/out.update-index'
+test_expect_success UPDATE_INDEX_OUT 'update-index output on unwritable repository' '
+	cat >expect <<-\EOF &&
+	error: insufficient permission for adding an object to repository database .git/objects
+	error: file: failed to insert into database
+	fatal: Unable to process path file
+	EOF
+	test_cmp expect out.update-index
 '
 
 test_expect_success POSIXPERM,SANITY 'add should notice unwritable repository' '
 	test_when_finished "chmod 775 .git/objects .git/objects/??" &&
 	echo b >file &&
 	chmod a-w .git/objects .git/objects/?? &&
-	test_must_fail git add file
+	test_must_fail git add file 2>out.add
+'
+
+test_lazy_prereq ADD_OUT 'test -e "$TRASH_DIRECTORY"/out.add'
+test_expect_success ADD_OUT 'add output on unwritable repository' '
+	cat >expect <<-\EOF &&
+	error: insufficient permission for adding an object to repository database .git/objects
+	error: file: failed to insert into database
+	error: unable to index file '\''file'\''
+	fatal: updating files failed
+	EOF
+	test_cmp expect out.add
 '
 
 test_done