Rebase without updating timestamps?

[mhkrebs]

Is there a way to do jj rebase or jj abandon without them updating timestamps of all the descendants?

In particular, I've got a commit with two parents from a month ago, and I want to rebase it to have just one parent. It's in an immutable "main" branch. Essentially:

- A - B ----- D - E -
       \- C -/

I want B to just have C as a parent (not D), although I'd also be fine with just abandoning B.

When I try something like jj rebase -r B -d C --ignore-immutable, it rebases as expected except jj log shows the timestamp of it and all its descendants being updated to the current time. I don't want that because it'll lose valuable information as to when commits were made.

I'm actually okay deleting that one commit completely, but something like jj abandon -r B also updates all the timestamps.

When I search around, I see claims that timestamps aren't supposed to be updated with jj, but that's not been my experience.

Am I missing something?

[jennings]

Git commits have two timestamps: the author timestamp and the committer timestamp.

jj updates only the committer time when rebasing, amending, etc. The author timestamp is preserved.

That's what people are likely referring to when they say timestamps aren't updated.

If you'd rather see author timestamps in your log output, you can change the commit_timestamp(commit) template alias to be commit.author().timestamp().

[mhkrebs]

Ah, thanks! It looks like git has --committer-date-is-author-date to change the committer time to match the author date.

Is there a way to do that with jj? It would be useful if at least jj metaedit had an option for that.