Thanks for working on this.
On Wed, Aug 6, 2014 at 7:59 PM, Fabian Ruch <bafain@xxxxxxxxx> wrote:
> The to-do list commands `squash` and `fixup` apply the changes
> introduced by the named commit to the tree but instead of creating
> a new commit on top of the current head it replaces the previous
> commit with a new commit that records the updated tree. If the
> result is an empty commit git-rebase stops with the error message
>
> You asked to amend the most recent commit, but doing so would make
> it empty. You can repeat your command with --allow-empty, or you can
> remove the commit entirely with "git reset HEAD^".
>
> This message is not very helpful because neither does git-rebase
> support an option `--allow-empty` nor does the messages say how to
> resume the rebase. Firstly, change the error message to
>
> The squash result is empty and --keep-empty was not specified.
>
> You can remove the squash commit now with
>
> git reset HEAD^
>
> Once you are down, run
s/down/done
>
> git rebase --continue
>
I like the direction of this rewording, but it seems to hide the
instructions for the user who wants to keep the empty commit.
I'm not sure how to improve it. Maybe this:
The squash result is empty and --keep-empty was not specified.
You may remove the squash commit now with
git reset HEAD^
or keep it by doing nothing extra.
Continue the rebase with
git rebase --continue
> If the user wishes to squash a sequence of commits into one
> commit, f. i.
>
> pick A
> squash Revert "A"
> squash A'
>
> , it does not matter for the end result that the first squash
> result, or any sub-sequence in general, is going to be empty. The
> squash message is not affected at all by which commits are created
> and only the commit created by the last line in the sequence will
> end up in the final history. Secondly, print the error message
> only if the whole squash sequence produced an empty commit.
>
> Lastly, since an empty squash commit is not a failure to rewrite
> the history as planned, issue the message above as a mere warning
> and interrupt the rebase with the return value zero. The
> interruption should be considered as a notification with the
> chance to undo it on the spot. Specifying the `--keep-empty`
> option tells git-rebase to keep empty squash commits in the
> rebased history without notification.
>
> Add tests.
>
> Reported-by: Peter Krefting <peter@xxxxxxxxxxxxxxxx>
> Signed-off-by: Fabian Ruch <bafain@xxxxxxxxx>
> ---
> Hi,
>
> Peter Krefting is cc'd as the author of the bug report "Confusing
> error message in rebase when commit becomes empty" discussed on the
> mailing list in June. Phil Hord and Jeff King both participated in
> the problem discussion which ended with two proposals by Jeff.
>
> Jeff King writes:
>> 1. Always keep such empty commits. A user who is surprised by them
>> being empty can then revisit them. Or drop them by doing another
>> rebase without --keep-empty.
>>
>> 2. Notice ourselves that the end-result of the whole squash is an
>> empty commit, and stop to let the user deal with it.
>
> This patch chooses the second alternative. Either way seems OK. The
> crucial consensus of the discussion was to silently throw away empty
> interim commits.
This patch does _not_ silently throw away empty commits. I wonder if
such behavior could be triggered with something like --no-keep-empty.
Maybe that belongs in another patch.
>
> Fabian
>
> git-rebase--interactive.sh | 20 +++++++++++---
> t/t3404-rebase-interactive.sh | 62 +++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 79 insertions(+), 3 deletions(-)
>
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 3222bf6..8820eac 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -549,7 +549,7 @@ do_next () {
> squash|s|fixup|f)
> # This is an intermediate commit; its message will only be
> # used in case of trouble. So use the long version:
> - do_with_author output git commit --allow-empty-message \
> + do_with_author output git commit --allow-empty-message --allow-empty \
> --amend --no-verify -F "$squash_msg" \
> ${gpg_sign_opt:+"$gpg_sign_opt"} ||
> die_failed_squash $sha1 "$rest"
> @@ -558,18 +558,32 @@ do_next () {
> # This is the final command of this squash/fixup group
> if test -f "$fixup_msg"
> then
> - do_with_author git commit --allow-empty-message \
> + do_with_author git commit --allow-empty-message --allow-empty \
> --amend --no-verify -F "$fixup_msg" \
> ${gpg_sign_opt:+"$gpg_sign_opt"} ||
> die_failed_squash $sha1 "$rest"
> else
> cp "$squash_msg" "$GIT_DIR"/SQUASH_MSG || exit
> rm -f "$GIT_DIR"/MERGE_MSG
> - do_with_author git commit --amend --no-verify -F "$GIT_DIR"/SQUASH_MSG -e \
> + do_with_author git commit --allow-empty --amend --no-verify -F "$GIT_DIR"/SQUASH_MSG -e \
> ${gpg_sign_opt:+"$gpg_sign_opt"} ||
> die_failed_squash $sha1 "$rest"
> fi
> rm -f "$squash_msg" "$fixup_msg"
> + if test -z "$keep_empty" && is_empty_commit HEAD
> + then
> + echo "$sha1" >"$state_dir"/stopped-sha
> + warn "The squash result is empty and --keep-empty was not specified."
> + warn
> + warn "You can remove the squash commit now with"
> + warn
> + warn " git reset HEAD^"
> + warn
> + warn "Once you are down, run"
s/down/done
> + warn
> + warn " git rebase --continue"
> + exit 0
> + fi
> ;;
> esac
> record_in_rewritten $sha1
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 9c71835..a95cb2a 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -237,6 +237,68 @@ test_expect_success 'retain authorship' '
> git show HEAD | grep "^Author: Twerp Snog"
> '
>
> +test_expect_success 'setup squash/fixup reverted and fixed feature' '
> + git checkout -b reverted-feature master &&
> + test_commit feature &&
> + git revert feature &&
> + git checkout -b fixed-feature reverted-feature &&
> + test_commit featurev2
> +'
> +
> +test_expect_success 'fixup fixed feature (empty interim commit)' '
> + git checkout -b fixup-fixed-feature fixed-feature &&
> + set_fake_editor &&
> + FAKE_LINES="1 fixup 2 fixup 3" git rebase -i master &&
> + git log --oneline master.. >actual &&
> + test_line_count = 1 actual &&
> + git diff --exit-code featurev2
> +'
> +
> +test_expect_success 'squash fixed feature (empty interim commit)' '
> + git checkout -b squash-fixed-feature fixed-feature &&
> + set_fake_editor &&
> + FAKE_LINES="1 squash 2 squash 3" git rebase -i master &&
> + git log --oneline master.. >actual &&
> + test_line_count = 1 actual &&
> + git diff --exit-code featurev2
> +'
> +
> +test_expect_success 'fixup reverted feature (empty final commit)' '
> + git checkout -b fixup-reverted-feature reverted-feature &&
> + set_fake_editor &&
> + FAKE_LINES="1 fixup 2" git rebase -i master &&
> + git reset HEAD^ &&
> + git rebase --continue &&
> + test_cmp_rev master HEAD
> +'
> +
> +test_expect_success 'squash reverted feature (empty final commit)' '
> + git checkout -b squash-reverted-feature reverted-feature &&
> + set_fake_editor &&
> + FAKE_LINES="1 squash 2" git rebase -i master &&
> + git reset HEAD^ &&
> + git rebase --continue &&
> + test_cmp_rev master HEAD
> +'
> +
> +test_expect_success 'fixup reverted feature (empty final commit with --keep-empty)' '
> + git checkout -b fixup-keep-reverted-feature reverted-feature &&
> + set_fake_editor &&
> + FAKE_LINES="1 fixup 2" git rebase -i --keep-empty master &&
> + git log --oneline master.. >actual &&
> + test_line_count = 1 actual &&
> + git diff --exit-code master
> +'
> +
> +test_expect_success 'squash reverted feature (empty final commit with --keep-empty)' '
> + git checkout -b squash-keep-reverted-feature reverted-feature &&
> + set_fake_editor &&
> + FAKE_LINES="1 squash 2" git rebase -i --keep-empty master &&
> + git log --oneline master.. >actual &&
> + test_line_count = 1 actual &&
> + git diff --exit-code master
> +'
> +
> test_expect_success 'squash' '
> git reset --hard twerp &&
> echo B > file7 &&
> --
> 2.0.1
>
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