From: Phillip Wood <phillip.wood123@gmail.com>
To: Junio C Hamano <gitster@pobox.com>,
Phillip Wood via GitGitGadget <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org,
Philippe Blain <levraiphilippeblain@gmail.com>,
Denton Liu <liu.denton@gmail.com>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>,
Phillip Wood <phillip.wood@dunelm.org.uk>
Subject: Re: [PATCH 3/5] rebase: factor out merge_base calculation
Date: Tue, 16 Aug 2022 14:50:05 +0100 [thread overview]
Message-ID: <c5b01472-7da9-6051-b127-1a8b8ddd2944@gmail.com> (raw)
In-Reply-To: <xmqqczd12zhv.fsf@gitster.g>
Hi Junio
On 15/08/2022 18:22, Junio C Hamano wrote:
> "Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
>> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>>
>> Separate out calculating the merge base between onto and head from the
>> check for whether we can fast-forward or not. This means we can skip
>> the fast-forward checks when the rebase is forced and avoid
>> calculating the merge-base twice when --keep-base is given.
I should clarify that this is referring to the merge base of onto and
upstream.
>>
>> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
>> ---
>> Note the unnecessary braces around "if (keep_base)" are added here
>> reduce the churn on the next commit.
>> ---
>> builtin/rebase.c | 35 +++++++++++++++++++++++------------
>> 1 file changed, 23 insertions(+), 12 deletions(-)
>>
>> diff --git a/builtin/rebase.c b/builtin/rebase.c
>> index 6cf9c95f4e1..86ea731ca3a 100644
>> --- a/builtin/rebase.c
>> +++ b/builtin/rebase.c
>> @@ -871,13 +871,9 @@ static int can_fast_forward(struct commit *onto, struct commit *upstream,
>> struct commit_list *merge_bases = NULL;
>> int res = 0;
>>
>> - merge_bases = get_merge_bases(onto, head);
>> - if (!merge_bases || merge_bases->next) {
>> - oidcpy(merge_base, null_oid());
>> + if (is_null_oid(merge_base))
>> goto done;
>> - }
>>
>> - oidcpy(merge_base, &merge_bases->item->object.oid);
>> if (!oideq(merge_base, &onto->object.oid))
>> goto done;
>
> Looking at the change in "git show -W", it seems that this function
> no longer touches merge_bases at all, other than initializing it to
> NULL at the beginning and then calling free_commit_list() on it at
> the end. Shouldn't it be removed?
There is still the line
merge_bases = get_merge_bases(upstream, head);
lower down. I should remove the call to free_commit_list() just above
that line though as it is no longer needed.
>> @@ -902,6 +898,20 @@ done:
>> return res && is_linear_history(onto, head);
>> }
>>
>> +static void fill_merge_base(struct rebase_options *options,
>> + struct object_id *merge_base)
>> +{
>> + struct commit_list *merge_bases = NULL;
>> +
>> + merge_bases = get_merge_bases(options->onto, options->orig_head);
>> + if (!merge_bases || merge_bases->next)
>> + oidcpy(merge_base, null_oid());
>> + else
>> + oidcpy(merge_base, &merge_bases->item->object.oid);
>> +
>> + free_commit_list(merge_bases);
>> +}
>> +
>> static int parse_opt_am(const struct option *opt, const char *arg, int unset)
>> {
>> struct rebase_options *opts = opt->value;
>> @@ -1668,7 +1678,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
>> die(_("Does not point to a valid commit '%s'"),
>> options.onto_name);
>> }
>> -
>> + if (keep_base) {
>> + oidcpy(&merge_base, &options.onto->object.oid);
This is actually unnecessary as we do
options.onto = lookup_commit_reference_by_name(options.onto_name);
above when calculating onto.
>> + } else {
>> + fill_merge_base(&options, &merge_base);
>> + }
>
> No need for braces around single-statement block on either side.
>
> This is not a new issue introduced by this patch per-se, but
> "merge_base" is becoming less and less accurate description of what
> this variable really is. Perhaps it is a good time to rename it?
Yes, merge_base is not a very descriptive name as it prompts the
question "merge base of which commits". I think base_commit or
branch_base would be better.
> It is "the base commit to rebuild the history on top of", aka "onto
> commit", isn't it?
I think it is the base commit of the branch i.e. we rebase all the
commits in the range merge_base..branch onto the "onto commit".
> We often use merge-base between the upstream and
> our tip of the history for it,
I'm pretty sure it is always the merge-base of the "onto commit" and our
tip of the history. When using --keep-base we calculate the "onto
commit" as the merge base of upstream and our tip of the history which
makes it look were using that for merge_base but that commit is also the
merge-base of the "onto commit" and our tip of history.
Best Wishes
Phillip
> but the variable often does not even
> hold the merge-base in it, not because we cannot compute a single
> merge-base but because depending on the operation mode we do not
> want to use merge-base for further operation using that variable.
next prev parent reply other threads:[~2022-08-16 13:50 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 15:11 [PATCH 0/5] rebase --keep-base: imply --reapply-cherry-picks and --no-fork-point Phillip Wood via GitGitGadget
2022-08-15 15:11 ` [PATCH 1/5] t3416: set $EDITOR in subshell Phillip Wood via GitGitGadget
2022-08-15 16:53 ` Junio C Hamano
2022-08-16 13:53 ` Phillip Wood
2022-08-24 22:28 ` Jonathan Tan
2022-08-30 15:12 ` Phillip Wood
2022-08-15 15:11 ` [PATCH 2/5] rebase: store orig_head as a commit Phillip Wood via GitGitGadget
2022-08-15 16:58 ` Junio C Hamano
2022-08-16 9:11 ` Johannes Schindelin
2022-08-18 7:01 ` Elijah Newren
2022-08-15 15:11 ` [PATCH 3/5] rebase: factor out merge_base calculation Phillip Wood via GitGitGadget
2022-08-15 17:22 ` Junio C Hamano
2022-08-16 9:15 ` Johannes Schindelin
2022-08-16 15:00 ` Junio C Hamano
2022-08-16 13:50 ` Phillip Wood [this message]
2022-08-16 15:03 ` Junio C Hamano
2022-08-18 7:11 ` Elijah Newren
2022-08-24 22:02 ` Jonathan Tan
2022-08-30 15:03 ` Phillip Wood
2022-08-15 15:11 ` [PATCH 4/5] rebase --keep-base: imply --reapply-cherry-picks Phillip Wood via GitGitGadget
2022-08-15 20:58 ` Junio C Hamano
2022-08-24 22:09 ` Jonathan Tan
2022-08-30 15:09 ` Phillip Wood
2022-08-25 0:29 ` Philippe Blain
2022-09-05 13:54 ` Phillip Wood
2022-08-15 15:11 ` [PATCH 5/5] rebase --keep-base: imply --no-fork-point Phillip Wood via GitGitGadget
2022-08-15 21:07 ` Junio C Hamano
2022-08-24 22:18 ` Jonathan Tan
2022-09-05 13:51 ` Phillip Wood
2022-08-16 9:23 ` [PATCH 0/5] rebase --keep-base: imply --reapply-cherry-picks and --no-fork-point Johannes Schindelin
2022-08-24 22:27 ` Jonathan Tan
2022-09-07 14:37 ` [PATCH v2 0/7] " Phillip Wood via GitGitGadget
2022-09-07 14:37 ` [PATCH v2 1/7] t3416: tighten two tests Phillip Wood via GitGitGadget
2022-09-07 18:12 ` Junio C Hamano
2022-09-07 14:37 ` [PATCH v2 2/7] t3416: set $EDITOR in subshell Phillip Wood via GitGitGadget
2022-09-07 18:12 ` Junio C Hamano
2022-09-07 14:37 ` [PATCH v2 3/7] rebase: store orig_head as a commit Phillip Wood via GitGitGadget
2022-09-07 18:12 ` Junio C Hamano
2022-09-08 13:19 ` Phillip Wood
2022-09-07 14:37 ` [PATCH v2 4/7] rebase: rename merge_base to branch_base Phillip Wood via GitGitGadget
2022-09-07 18:12 ` Junio C Hamano
2022-09-07 14:37 ` [PATCH v2 5/7] rebase: factor out branch_base calculation Phillip Wood via GitGitGadget
2022-09-07 18:12 ` Junio C Hamano
2022-09-07 14:37 ` [PATCH v2 6/7] rebase --keep-base: imply --reapply-cherry-picks Phillip Wood via GitGitGadget
2022-09-07 14:37 ` [PATCH v2 7/7] rebase --keep-base: imply --no-fork-point Phillip Wood via GitGitGadget
2022-09-08 2:44 ` Denton Liu
2022-09-08 13:21 ` Phillip Wood
2022-10-13 8:42 ` [PATCH v3 0/8] rebase --keep-base: imply --reapply-cherry-picks and --no-fork-point Phillip Wood via GitGitGadget
2022-10-13 8:42 ` [PATCH v3 1/8] t3416: tighten two tests Phillip Wood via GitGitGadget
2022-10-13 8:42 ` [PATCH v3 2/8] t3416: set $EDITOR in subshell Phillip Wood via GitGitGadget
2022-10-13 8:42 ` [PATCH v3 3/8] rebase: be stricter when reading state files containing oids Phillip Wood via GitGitGadget
2022-10-13 16:34 ` Junio C Hamano
2022-10-13 19:10 ` Ævar Arnfjörð Bjarmason
2022-10-13 20:13 ` Junio C Hamano
2022-10-13 8:42 ` [PATCH v3 4/8] rebase: store orig_head as a commit Phillip Wood via GitGitGadget
2022-10-13 16:34 ` Junio C Hamano
2022-10-13 20:49 ` Phillip Wood
2022-10-13 23:25 ` Junio C Hamano
2022-10-13 8:42 ` [PATCH v3 5/8] rebase: rename merge_base to branch_base Phillip Wood via GitGitGadget
2022-10-13 19:16 ` Ævar Arnfjörð Bjarmason
2022-10-17 9:49 ` Phillip Wood
2022-10-17 11:27 ` Ævar Arnfjörð Bjarmason
2022-10-17 13:13 ` Phillip Wood
2022-10-17 16:19 ` Ævar Arnfjörð Bjarmason
2022-10-19 15:35 ` Phillip Wood
2022-10-13 8:42 ` [PATCH v3 6/8] rebase: factor out branch_base calculation Phillip Wood via GitGitGadget
2022-10-13 19:21 ` Ævar Arnfjörð Bjarmason
2022-10-17 9:39 ` Phillip Wood
2022-10-17 11:23 ` Ævar Arnfjörð Bjarmason
2022-10-13 8:42 ` [PATCH v3 7/8] rebase --keep-base: imply --reapply-cherry-picks Phillip Wood via GitGitGadget
2022-10-13 8:42 ` [PATCH v3 8/8] rebase --keep-base: imply --no-fork-point Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 0/8] rebase --keep-base: imply --reapply-cherry-picks and --no-fork-point Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 1/8] t3416: tighten two tests Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 2/8] t3416: set $EDITOR in subshell Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 3/8] rebase: be stricter when reading state files containing oids Phillip Wood via GitGitGadget
2022-10-17 18:51 ` Junio C Hamano
2022-10-19 15:32 ` Phillip Wood
2022-10-17 13:17 ` [PATCH v4 4/8] rebase: store orig_head as a commit Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 5/8] rebase: rename merge_base to branch_base Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 6/8] rebase: factor out branch_base calculation Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 7/8] rebase --keep-base: imply --reapply-cherry-picks Phillip Wood via GitGitGadget
2022-10-17 13:17 ` [PATCH v4 8/8] rebase --keep-base: imply --no-fork-point Phillip Wood via GitGitGadget
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