git squash and preserve last commit's timestamp

Question

Consider I have commits

... -- A -- B -- C 

If I use git rebase -i to squash all three commits into one, we could

pick A squash B squash C 

I see the resulted commit A has its original timestamp. How could make it inherit the timestamp of commit C (the last one)?

What I can think of is git commit --amend --date=<new_time>, but this way needs to remember the timestamp of commit C before squash or from reflog.

I find the timestamp of the latest commit is more reasonable, because it shows when I actually finished the work that are in the commits.

Thanks.

Answer 1

There's not a trivial way to do this, but there are a few options. Here's one:

git commit --amend --date="$(git show -s --pretty=tformat:%ai <sha1-of-C>)" 

And another:

git commit --amend -c <sha1-of-C> 

The latter will clobber your existing commit message, so you'll have to rewrite it.