From: Phillip Wood Date: Thu, 19 Aug 2021 10:09:26 GMT Subject: Re: [PATCH 3/4] rebase -r: don't write .git/MERGE_MSG when fast-forwarding Message-ID: <49aba79b-14ed-cee0-4e4c-1f98306f1b45@gmail.com> In-Reply-To: <20210817172609.GB2257957@szeder.dev> On 17/08/2021 18:26, SZEDER Gábor wrote: > On Fri, Aug 13, 2021 at 01:07:32PM +0000, Phillip Wood via GitGitGadget wrote: >> From: Phillip Wood >> >> When fast-forwarding we do not create a new commit so .git/MERGE_MSG >> is not removed and can end up seeding the message of a commit made >> after the rebase has finished. Avoid writing .git/MERGE_MSG when we >> are fast-forwarding by writing the file after the fast-forward >> checks. >> >> Note that the way this change is implemented means we no longer write >> the author script when fast-forwarding either. I believe this is safe >> for the reasons below but it is a departure from what we do when >> fast-forwarding a non-merge commit. If we reword the merge then 'git >> commit --amend' will keep the authorship of the commit we're rewording >> as it ignores GIT_AUTHOR_* unless --reset-author is passed. It will >> also export the correct GIT_AUTHOR_* variables to any hooks and we >> already test the authorship of the reworded commit. If we are not >> rewording then we no longer call spilt_ident() which means we are no >> longer checking the commit author header looks sane. However this is >> what we already do when fast-forwarding non-merge commits in >> skip_unnecessary_picks() so I don't think we're breaking any promises >> by not checking the author here. > > Thanks you for fixing this bug. > > FWIW (not that much, I'm afraid), I think your reasoning about the > harmlessness of the behavior change concerning the author script makes > sense. > > My only nit is that the movement of a ~40 lines block of code makes > out the bulk of the patch; perhaps it would be worth mentioning it > explicitly in the commit message, so future readers of this commit > won't look for changes in those hunks. Thanks for reading through the patch, I take your point about the code movement and will add a comment (I have --color-moved turned on by default and tend to forget others may not) Best Wishes Phillip >> Reported-by: SZEDER Gábor >> Signed-off-by: Phillip Wood >> --- >> sequencer.c | 81 +++++++++++++++++++++++++------------------------ >> t/lib-rebase.sh | 10 ++++-- >> 2 files changed, 49 insertions(+), 42 deletions(-) >> >> diff --git a/sequencer.c b/sequencer.c >> index cc8a361cceb..c2cba5ed4b1 100644 >> --- a/sequencer.c >> +++ b/sequencer.c >> @@ -983,7 +983,8 @@ static int run_git_commit(const char *defmsg, >> >> cmd.git_cmd = 1; >> >> - if (is_rebase_i(opts) && read_env_script(&cmd.env_array)) { >> + if (is_rebase_i(opts) && !(!defmsg && (flags & AMEND_MSG)) && >> + read_env_script(&cmd.env_array)) { >> const char *gpg_opt = gpg_sign_opt_quoted(opts); >> >> return error(_(staged_changes_advice), >> @@ -3815,6 +3816,45 @@ static int do_merge(struct repository *r, >> goto leave_merge; >> } >> >> + /* >> + * If HEAD is not identical to the first parent of the original merge >> + * commit, we cannot fast-forward. >> + */ >> + can_fast_forward = opts->allow_ff && commit && commit->parents && >> + oideq(&commit->parents->item->object.oid, >> + &head_commit->object.oid); >> + >> + /* >> + * If any merge head is different from the original one, we cannot >> + * fast-forward. >> + */ >> + if (can_fast_forward) { >> + struct commit_list *p = commit->parents->next; >> + >> + for (j = to_merge; j && p; j = j->next, p = p->next) >> + if (!oideq(&j->item->object.oid, >> + &p->item->object.oid)) { >> + can_fast_forward = 0; >> + break; >> + } >> + /* >> + * If the number of merge heads differs from the original merge >> + * commit, we cannot fast-forward. >> + */ >> + if (j || p) >> + can_fast_forward = 0; >> + } >> + >> + if (can_fast_forward) { >> + rollback_lock_file(&lock); >> + ret = fast_forward_to(r, &commit->object.oid, >> + &head_commit->object.oid, 0, opts); >> + if (flags & TODO_EDIT_MERGE_MSG) >> + goto fast_forward_edit; >> + >> + goto leave_merge; >> + } >> + >> if (commit) { >> const char *encoding = get_commit_output_encoding(); >> const char *message = logmsg_reencode(commit, NULL, encoding); >> @@ -3864,45 +3904,6 @@ static int do_merge(struct repository *r, >> } >> } >> >> - /* >> - * If HEAD is not identical to the first parent of the original merge >> - * commit, we cannot fast-forward. >> - */ >> - can_fast_forward = opts->allow_ff && commit && commit->parents && >> - oideq(&commit->parents->item->object.oid, >> - &head_commit->object.oid); >> - >> - /* >> - * If any merge head is different from the original one, we cannot >> - * fast-forward. >> - */ >> - if (can_fast_forward) { >> - struct commit_list *p = commit->parents->next; >> - >> - for (j = to_merge; j && p; j = j->next, p = p->next) >> - if (!oideq(&j->item->object.oid, >> - &p->item->object.oid)) { >> - can_fast_forward = 0; >> - break; >> - } >> - /* >> - * If the number of merge heads differs from the original merge >> - * commit, we cannot fast-forward. >> - */ >> - if (j || p) >> - can_fast_forward = 0; >> - } >> - >> - if (can_fast_forward) { >> - rollback_lock_file(&lock); >> - ret = fast_forward_to(r, &commit->object.oid, >> - &head_commit->object.oid, 0, opts); >> - if (flags & TODO_EDIT_MERGE_MSG) >> - goto fast_forward_edit; >> - >> - goto leave_merge; >> - } >> - >> if (strategy || to_merge->next) { >> /* Octopus merge */ >> struct child_process cmd = CHILD_PROCESS_INIT; >> diff --git a/t/lib-rebase.sh b/t/lib-rebase.sh >> index 99d9e7efd2d..ec6b9b107da 100644 >> --- a/t/lib-rebase.sh >> +++ b/t/lib-rebase.sh >> @@ -173,10 +173,16 @@ set_reword_editor () { >> >> write_script reword-editor.sh <<-EOF && >> # Save the oid of the first reworded commit so we can check rebase >> - # fast-forwards to it >> + # fast-forwards to it. Also check that we do not write .git/MERGE_MSG >> + # when fast-forwarding >> if ! test -s reword-oid >> then >> - git rev-parse HEAD >reword-oid >> + git rev-parse HEAD >reword-oid && >> + if test -f .git/MERGE_MSG >> + then >> + echo 1>&2 "error: .git/MERGE_MSG exists" >> + exit 1 >> + fi >> fi && >> # There should be no uncommited changes >> git diff --exit-code HEAD && >> -- >> gitgitgadget >>