Re: [PATCH v7 0/5] history: add squash subcommand to fold a range

>  3:  811e393ab4 ! 3:  cf3346a1cd history: add squash subcommand to fold a range
>      @@ Commit message
>           Add "git history squash <revision-range>" to do this directly. It folds
>           every commit in the range into the oldest one, keeping that commit's
>           message and authorship and taking the tree of the newest commit, then
>      -    replays the commits above the range on top. fixup!, squash! and amend!
>      -    commits are folded like any other and are not interpreted, so the
>      -    squashed message comes from the oldest commit, or from an editor with
>      -    --reedit-message.
>      +    replays the commits above the range on top. The squashed message comes
>      +    from the oldest commit, or from an editor with --reedit-message. As that
>      +    message is reused, a range whose oldest commit is a fixup!, squash! or
>      +    amend! is refused, since the marker's target cannot be in the range.
> ...
>      -+git history squash <revision-range> [--dry-run] [--update-refs=(branches|head)] [--reedit-message]
>      ++git history squash [--dry-run] [--update-refs=(branches|head)] [--reedit-message] <revision-range>

>      ++static int reject_fixupish_oldest(struct repository *repo,
>      ++				  struct commit *oldest)
>      ++{
>      ++	const char *message, *subject;
>      ++	int ret = 0;
>      ++
>      ++	message = repo_logmsg_reencode(repo, oldest, NULL, NULL);
>      ++	find_commit_subject(message, &subject);
>      ++	if (starts_with(subject, "fixup! ") ||
>      ++	    starts_with(subject, "squash! ") ||
>      ++	    starts_with(subject, "amend! "))
>      ++		ret = error(_("the range begins with a fixup!, squash! or amend! "
>      ++			      "commit whose target is not in the range"));
>      ++	repo_unuse_commit_buffer(repo, oldest, message);
>      ++	return ret;
>      ++}