Re: [PATCH] Teach checkout the -n|--dry-run option

Jens Lehmann [off-list ref] writes:

That's a rather sloppy way to test that the command did not do anything to
compare one possible outcome, instead of verifying that the result is
identical to the original condition, no?

How about

	...
	git update_index --add AA &&
        git ls-files -s >pre-dry-run &&
        git read-tree -n -m $tree_O $tree_A $tree_B &&
        git ls-files -s >post-dry-run &&
        test_cmp pre-dry-run post-dry-run &&
        ...

We also should be checking that the command reports it is going to fail
when it should as well.  Always remember to check both sides of the coin.

      git read-tree -m $tree_O $tree_A $tree_B &&
      check_result"

I suspect that it would make sense to replace

	git read-tree $args && check_result

with
        
	read_tree_must_succeed $args

and

	test_must_fail git read-tree $args

with

	read_tree_must_fail $args

and implement two shell wrappers, perhaps like this.

read_tree_must_succeed () {
	git ls-files -s >pre-dry-run &&
	git read-tree -n "$@" &&
        git ls-files -s >post-dry-run &&
        test_cmp pre-dry-run post-dry-run &&
        git read-tree "$@"
}

read_tree_must_fail () {
	git ls-files -s >pre-dry-run &&
	test_must_fail git read-tree -n "$@" &&
        git ls-files -s >post-dry-run &&
	test_must_fail git read-tree "$@"
}