Re: what should "git clean -n -f [-d] [-x] <pattern>" do?

Sergey Organov <sorganov@gmail.com> writes:

Not so fast. I said "if the original semantics were ... then it would have led to the above behaviour". As the original semantics were not, that conclusion does not stand.

The "-n" option here were not added primarily as a dry-run option, and haven't been treated as such forever. As can be seen by the "you must give either -f or -n option, and it is an error to give neither" rule, from the end-user's point of view, it is a way to say "between do-it (-f) and do-not-do-it (-n), I choose the latter for this invocation". And in that context, an attempt to make "-f -f" mean a stronger form of forcing than "-f" was a mistake, because it makes your "I want to see what happens if I tried that opration that requires the stronger force" request impossible.

And there are two equally valid ways to deal with this misfeature.

One is to admit that "-f -f" was a mistake (which I already said), and a natural consequence of that admission is to introduce a more specific "in addition to what you do usually, this riskier operation is allowed" option (e.g., --nested-repo). This leads to a design that matches real world usage better, even if we did not have the "how to ask dry-run?" issue, because in the real world, when there are multiple "risky" things you may have to explicitly ask to enable, these things do not necessarily form a nice linear "riskiness levels" that you can express your risk tolerance with the number of "-f" options. When you need to add special protection for a new case other than "nested repo", for example, the "riskiness levels" design may need to place it above the "nested repo" level of riskiness and may require the user to give three "-f" options, but that would make it impossible to protect against nuking of nested repos while allowing only that newly added case. By having more specific "this particular risky operation is allowed", "-f" can still be "between do-it and do-not-do-it, I choose the former", and the "--nested-repo" (and other options to allow specific risky operations we add in the future) would not have to have funny interactions with "-n".

The other valid way is to treat the use of the "riskiness levels" to specify what is forced still as a good idea. If one comes from that position, the resulting UI would be consistent with what you have been advocating for. One or more "-f" will specify what kind of risky stuff are allowed, and "-n" will say whether the operation gets carried out or merely shown what would happen if "-n" weren't there.

It is just that I think "riskiness levels" I did in a0f4afbe (clean: require double -f options to nuke nested git repository and work tree, 2009-06-30) was an utter mistake, and that is why I feel very hesitant to agree with the design that still promotes it.