Re: why is git destructive by default? (i suggest it not be!)

I'm not talking about switching "git reset --hard" to "git reset -f". I'm talking about requiring a "-f" option to "git reset --hard" when it would destroy or dangle information.

(a) If you have a clean working directory which is fully checked in and has another branch tag other than the current branch tag, then "git reset --hard <commitish>" is non-destructive, and would complete happily.

(b) If you have local modifications to working files it would complain "hey, your working files are dirty, 'reset --hard' will blow them away, either revert them or use -f". This is what Boaz asked for, and I doubt it would change along would alter workflow much for people who are using "git reset --hard" to toss attempted patches (since they were fully committed anyhow), or even undo a clone or pull operation. If people use it as a combo "revert and reset", they would notice.

(c) If the current location is only pointed to by the current branch (which you are going to move with 'reset --hard') tell the user that those changes will be dangling and will be eligible for garbage collection if they move the branch. What to do in this case seems more controversial. I would prefer for this to error with "either label these changes with 'branch', or use 'reset --hard -f' to force us to leave these in the reflog unnamed". --- Some here say that being in the reflog is enough, and the -f is overkill here. If we define destructive as dropping code-commits, then that's true. If we define destructive as leaving code-commits unreferenced, then -f is warranted. Personally, I'd rather git help me avoid dropping the NAMES to tips, because even with GC-never, I don't really want to find myself crawling through SHA1 hashes and visualization trees to find them later, when git could have reminded me to name a branch that would conveniently show up in 'git branch'. It's easy enough to avoid dropping the names, or force git to not care with '-f'. I personally would like to avoid dealing with reflog or SHA1 hashes 99% of the time.

This was an accident. When I made my "mv --aggressive" joke I was NOT intending to reference "gc --aggressive", that is just a coincidence. I was trying to make up another 'semi-dangerous sounding name that might or not might be destructive". It's comical that it's in use for gc. I don't see any relationship between "gc --aggressive" and destructive behavior.

However, there IS a situation to require a "-f" on a, because again, "-f" would be required for operations which destroy commits. If we think commits being in the reflog is good enough to hold onto them, and users are thinking that items being in the reflog are 'safe', then a GC where reflog entry expiration is going to cause DAG entries to be removed could print an error like:

error: the following entries are beyond the expiration time, ...<base branchname>/<commit-ish>: 17 commits, 78 lines, 3 authors ...use diff <commit-ish> , to see the changes ...use gc -f, to cause them to be deleted

This wouldn't happen very often, and would make "gc" a safe operation even on trees with shorter expiration time. In fact, if this were the way it worked, I might set my GC back from never to "30 days", because this would not only allow me to safely cleanup junk, but it would also allow me to catch unnamed and dangling references before they became so old I didn't remember what to name them.

This would make a "non forced gc" safe from throwing away commits, but still make it really easy to do so for people who want to. Likewise, we could make any "auto-gc" that happens not forced by default.