From: Phillip Wood Date: Wed, 17 Apr 2019 19:59:09 GMT Subject: Re: [PATCH v6 4/6] rebase: fast-forward --onto in more cases Message-ID: In-Reply-To: <2559ab54a2c6e5544595e0d66a431e249bf73ca8.1555523176.git.liu.denton@gmail.com> Hi Denton On 17/04/2019 19:01, Denton Liu wrote: > Before, when we had the following graph, > > A---B---C (master) > \ > D (side) > > running 'git rebase --onto master... master side' would result in D > being always rebased, no matter what. However, the desired behavior is > that rebase should notice that this is fast-forwardable and do that > instead. > > Add detection to `can_fast_forward` so that this case can be detected > and a fast-forward will be performed. First of all, rewrite the function > to use gotos which simplifies the logic. Next, since the > > options.upstream && > !oidcmp(&options.upstream->object.oid, &options.onto->object.oid) > > conditions were removed in `cmd_rebase`, we reintroduce a substitute in > `can_fast_forward`. In particular, checking the merge bases of > `upstream` and `head` fixes a failing case in t3416. > > The abbreviated graph for t3416 is as follows: > > F---G topic > / > A---B---C---D---E master > > and the failing command was > > git rebase --onto master...topic F topic > > Before, Git would see that there was one merge base (C), and the merge > and onto were the same so it would incorrectly return 1, indicating that > we could fast-forward. This would cause the rebased graph to be 'ABCFG' > when we were expecting 'ABCG'. > > With the additional logic, we detect that upstream and head's merge base > is F. Since onto isn't F, it means we're not rebasing the full set of > commits from master..topic. Since we're excluding some commits, a > fast-forward cannot be performed and so we correctly return 0. > > Add '-f' to test cases that failed as a result of this change because > they were not expecting a fast-forward so that a rebase is forced. > > While we're at it, remove a trailing whitespace from rebase.c. > > Helped-by: Phillip Wood > Signed-off-by: Denton Liu > --- > builtin/rebase.c | 28 +++++++++++++++++++--------- > t/t3400-rebase.sh | 2 +- > t/t3404-rebase-interactive.sh | 2 +- > t/t3432-rebase-fast-forward.sh | 4 ++-- > 4 files changed, 23 insertions(+), 13 deletions(-) > > diff --git a/builtin/rebase.c b/builtin/rebase.c > index de10b6f5ad..f5aca1eee0 100644 > --- a/builtin/rebase.c > +++ b/builtin/rebase.c > @@ -895,8 +895,8 @@ static int is_linear_history(struct commit *from, struct commit *to) > return 1; > } > > -static int can_fast_forward(struct commit *onto, struct object_id *head_oid, > - struct object_id *merge_base) > +static int can_fast_forward(struct commit *onto, struct commit *upstream, > + struct object_id *head_oid, struct object_id *merge_base) > { > struct commit *head = lookup_commit(the_repository, head_oid); > struct commit_list *merge_bases = NULL; > @@ -915,6 +915,18 @@ static int can_fast_forward(struct commit *onto, struct object_id *head_oid, > if (!oideq(merge_base, &onto->object.oid)) > goto done; > > + if (!upstream) > + goto done; > + > + free_commit_list(merge_bases); > + merge_bases = get_merge_bases(upstream, head); > + if (!merge_bases || merge_bases->next) { > + goto done; > + } Thanks for changing the ifs in this patch and the previous one, I find it much easier to follow now. Just one style nit (probably not worth a reroll) - we don't put braces around a single conditional statement like this unless another branch of the same if requires them (then all branches should have them). Best Wishes Phillip > + > + if (!oideq(&onto->object.oid, &merge_bases->item->object.oid)) > + goto done; > + > res = 1; > > done: > @@ -1688,13 +1700,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix) > > /* > * Check if we are already based on onto with linear history, > - * but this should be done only when upstream and onto are the same > - * and if this is not an interactive rebase. > + * but this should be done if this is not an interactive rebase. > */ > - if (can_fast_forward(options.onto, &options.orig_head, &merge_base) && > - !is_interactive(&options) && !options.restrict_revision && > - options.upstream && > - !oidcmp(&options.upstream->object.oid, &options.onto->object.oid)) { > + if (can_fast_forward(options.onto, options.upstream, &options.orig_head, > + &merge_base) && > + !is_interactive(&options) && !options.restrict_revision) { > int flag; > > if (!(options.flags & REBASE_FORCE)) { > @@ -1788,7 +1798,7 @@ int cmd_rebase(int argc, const char **argv, const char *prefix) > strbuf_addf(&msg, "%s: checkout %s", > getenv(GIT_REFLOG_ACTION_ENVIRONMENT), options.onto_name); > if (reset_head(&options.onto->object.oid, "checkout", NULL, > - RESET_HEAD_DETACH | RESET_ORIG_HEAD | > + RESET_HEAD_DETACH | RESET_ORIG_HEAD | > RESET_HEAD_RUN_POST_CHECKOUT_HOOK, > NULL, msg.buf)) > die(_("Could not detach HEAD")); > diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh > index 460d0523be..604d624ff8 100755 > --- a/t/t3400-rebase.sh > +++ b/t/t3400-rebase.sh > @@ -295,7 +295,7 @@ test_expect_success 'rebase--am.sh and --show-current-patch' ' > echo two >>init.t && > git commit -a -m two && > git tag two && > - test_must_fail git rebase --onto init HEAD^ && > + test_must_fail git rebase -f --onto init HEAD^ && > GIT_TRACE=1 git rebase --show-current-patch >/dev/null 2>stderr && > grep "show.*$(git rev-parse two)" stderr > ) > diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh > index b60b11f9f2..f054186cc7 100755 > --- a/t/t3404-rebase-interactive.sh > +++ b/t/t3404-rebase-interactive.sh > @@ -1066,7 +1066,7 @@ test_expect_success C_LOCALE_OUTPUT 'rebase --edit-todo does not work on non-int > git reset --hard && > git checkout conflict-branch && > set_fake_editor && > - test_must_fail git rebase --onto HEAD~2 HEAD~ && > + test_must_fail git rebase -f --onto HEAD~2 HEAD~ && > test_must_fail git rebase --edit-todo && > git rebase --abort > ' > diff --git a/t/t3432-rebase-fast-forward.sh b/t/t3432-rebase-fast-forward.sh > index 4f04d67fd7..d0e5b1f3e6 100755 > --- a/t/t3432-rebase-fast-forward.sh > +++ b/t/t3432-rebase-fast-forward.sh > @@ -64,9 +64,9 @@ test_expect_success 'add work to upstream' ' > changes='our and their changes' > test_rebase_same_head success --onto B B > test_rebase_same_head success --onto B... B > -test_rebase_same_head failure --onto master... master > +test_rebase_same_head success --onto master... master > test_rebase_same_head failure --fork-point --onto B B > test_rebase_same_head failure --fork-point --onto B... B > -test_rebase_same_head failure --fork-point --onto master... master > +test_rebase_same_head success --fork-point --onto master... master > > test_done >