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From: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
To: git@vger.kernel.org
Cc: "Junio C Hamano" <gitster@pobox.com>,
	"Denton Liu" <liu.denton@gmail.com>,
	"Eric Sunshine" <sunshine@sunshineco.com>,
	"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
	"Johannes Sixt" <j6t@kdbg.org>,
	"SZEDER Gábor" <szeder.dev@gmail.com>,
	"Phillip Wood" <phillip.wood@dunelm.org.uk>
Subject: [RFC WIP PATCH v8 06/13] rebase: fast-forward --onto in more cases
Date: Wed,  8 May 2019 02:12:45 +0200	[thread overview]
Message-ID: <20190508001252.15752-7-avarab@gmail.com> (raw)
In-Reply-To: <cover.1555832783.git.liu.denton@gmail.com>

From: Denton Liu <liu.denton@gmail.com>

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 <phillip.wood@dunelm.org.uk>
Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/rebase.c               | 29 ++++++++++++++++++++---------
 t/t3400-rebase.sh              |  2 +-
 t/t3404-rebase-interactive.sh  |  2 +-
 t/t3432-rebase-fast-forward.sh |  4 ++--
 4 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index f7008b10af..c1000c159d 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -878,8 +878,8 @@ 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;
@@ -898,6 +898,17 @@ 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;
+
+	if (!oideq(&onto->object.oid, &merge_bases->item->object.oid))
+		goto done;
+
 	res = 1;
 
 done:
@@ -1664,13 +1675,13 @@ 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.
+	 * in which case we could fast-forward without replacing the commits
+	 * with new commits recreated by replaying their changes. This
+	 * optimization must not be done if this is 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)) {
@@ -1764,7 +1775,7 @@ 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 42f147858d..45f1f65c7b 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 1723e1a858..c7dbbd16db 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -1063,7 +1063,7 @@ 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 e20a8ab9c4..59cd437301 100755
--- a/t/t3432-rebase-fast-forward.sh
+++ b/t/t3432-rebase-fast-forward.sh
@@ -106,9 +106,9 @@ test_expect_success 'add work same  to upstream' '
 changes='our and their changes'
 test_rebase_same_head success noop same success noop-force diff --onto B B
 test_rebase_same_head success noop same success noop-force diff --onto B... B
-test_rebase_same_head failure work same success work diff --onto master... master
+test_rebase_same_head success noop same success work diff --onto master... master
 test_rebase_same_head failure work same success work diff --fork-point --onto B B
 test_rebase_same_head failure work same success work diff --fork-point --onto B... B
-test_rebase_same_head failure work same success work diff --fork-point --onto master... master
+test_rebase_same_head success noop same success work diff --fork-point --onto master... master
 
 test_done
-- 
2.21.0.1020.gf2820cf01a


  parent reply	other threads:[~2019-05-08  0:13 UTC|newest]

Thread overview: 123+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-23 15:25 [PATCH 0/3] rebase: learn --keep-base Denton Liu
2019-03-23 15:25 ` [PATCH 1/3] rebase: teach rebase --keep-base Denton Liu
2019-03-24  3:46   ` Eric Sunshine
2019-03-24 13:20   ` Junio C Hamano
2019-03-25  0:06     ` Denton Liu
2019-03-25  5:41       ` Denton Liu
2019-04-01 10:45         ` Junio C Hamano
2019-03-24 13:37   ` Junio C Hamano
2019-03-25  5:47   ` Denton Liu
2019-03-25 18:50   ` Johannes Schindelin
2019-03-25 19:29     ` Denton Liu
2019-03-26 13:27       ` Johannes Schindelin
2019-03-23 15:25 ` [PATCH 2/3] t3416: test " Denton Liu
2019-03-23 15:25 ` [PATCH 3/3] git-rebase.txt: document --keep-base option Denton Liu
2019-03-24 13:15 ` [PATCH 0/3] rebase: learn --keep-base Junio C Hamano
2019-03-25  0:04   ` Denton Liu
2019-04-01 10:45     ` Junio C Hamano
2019-03-26 14:35 ` Ævar Arnfjörð Bjarmason
2019-03-26 17:50   ` Denton Liu
2019-03-26 20:35     ` Ævar Arnfjörð Bjarmason
2019-03-26 21:30       ` Denton Liu
2019-03-27 15:39         ` Ævar Arnfjörð Bjarmason
2019-03-28 22:17 ` [PATCH v2] rebase: teach rebase --keep-base Denton Liu
2019-03-28 23:13   ` Ævar Arnfjörð Bjarmason
2019-03-29 15:47   ` Johannes Schindelin
2019-03-29 17:52     ` Denton Liu
2019-04-01 10:46     ` Junio C Hamano
2019-04-01 20:51   ` [PATCH v3 0/4] " Denton Liu
2019-04-01 20:51     ` [PATCH v3 1/4] t3431: add rebase --fork-point tests Denton Liu
2019-04-04 20:28       ` Denton Liu
2019-04-05 11:15       ` SZEDER Gábor
2019-04-08  4:38         ` Junio C Hamano
2019-04-05 14:55       ` Johannes Schindelin
2019-04-05 17:25         ` Denton Liu
2019-04-05 17:51           ` Johannes Sixt
2019-04-05 18:51             ` Johannes Schindelin
2019-04-05 20:19               ` Johannes Schindelin
2019-04-05 21:10                 ` SZEDER Gábor
2019-04-01 20:51     ` [PATCH v3 2/4] t3432: test rebase fast-forward behavior Denton Liu
2019-04-01 20:52     ` [PATCH v3 3/4] rebase: fast-forward --onto in more cases Denton Liu
2019-04-02  1:25       ` Junio C Hamano
2019-04-02  1:48         ` Junio C Hamano
2019-04-02  4:44           ` Denton Liu
2019-04-01 20:52     ` [PATCH v3 4/4] rebase: teach rebase --keep-base Denton Liu
2019-04-05 21:39     ` [PATCH v4 0/4] " Denton Liu
2019-04-05 21:40       ` [PATCH v4 1/4] t3431: add rebase --fork-point tests Denton Liu
2019-04-05 21:40       ` [PATCH v4 2/4] t3432: test rebase fast-forward behavior Denton Liu
2019-04-05 21:40       ` [PATCH v4 3/4] rebase: fast-forward --onto in more cases Denton Liu
2019-04-05 21:40       ` [PATCH v4 4/4] rebase: teach rebase --keep-base Denton Liu
2019-04-15 22:29       ` [PATCH v5 0/5] " Denton Liu
2019-04-15 22:29         ` [PATCH v5 1/5] t3431: add rebase --fork-point tests Denton Liu
2019-04-15 22:29         ` [PATCH v5 2/5] t3432: test rebase fast-forward behavior Denton Liu
2019-04-15 22:29         ` [PATCH v5 3/5] rebase: fast-forward --onto in more cases Denton Liu
2019-04-16  6:26           ` Junio C Hamano
2019-04-16 13:59           ` Phillip Wood
2019-04-17  6:44             ` Denton Liu
2019-04-17 14:14               ` Phillip Wood
2019-04-19 17:08           ` Denton Liu
2019-04-15 22:29         ` [PATCH v5 4/5] rebase: fast-forward --fork-point " Denton Liu
2019-04-15 22:29         ` [PATCH v5 5/5] rebase: teach rebase --keep-base Denton Liu
2019-04-17 18:01       ` [PATCH v6 0/5] " Denton Liu
2019-04-17 18:01         ` [PATCH v6 1/6] t3431: add rebase --fork-point tests Denton Liu
2019-04-17 18:01         ` [PATCH v6 2/6] t3432: test rebase fast-forward behavior Denton Liu
2019-04-17 18:01         ` [PATCH v6 3/6] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-04-17 18:01         ` [PATCH v6 4/6] rebase: fast-forward --onto in more cases Denton Liu
2019-04-17 19:59           ` Phillip Wood
2019-04-17 18:01         ` [PATCH v6 5/6] rebase: fast-forward --fork-point " Denton Liu
2019-04-17 18:01         ` [PATCH v6 6/6] rebase: teach rebase --keep-base Denton Liu
2019-04-21  8:11         ` [PATCH v7 0/6] rebase: learn --keep-base Denton Liu
2019-04-21  8:11           ` [PATCH v7 1/6] t3431: add rebase --fork-point tests Denton Liu
2019-04-23 23:12             ` Denton Liu
2019-04-21  8:11           ` [PATCH v7 2/6] t3432: test rebase fast-forward behavior Denton Liu
2019-04-21  8:11           ` [PATCH v7 3/6] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-04-21  8:11           ` [PATCH v7 4/6] rebase: fast-forward --onto in more cases Denton Liu
2019-04-21  8:11           ` [PATCH v7 5/6] rebase: fast-forward --fork-point " Denton Liu
2019-04-21  8:11           ` [PATCH v7 6/6] rebase: teach rebase --keep-base Denton Liu
2019-05-08  0:12           ` [RFC WIP PATCH v8 00/13] learn --keep-base & more Ævar Arnfjörð Bjarmason
2019-05-08  3:57             ` Junio C Hamano
2019-07-19 19:14               ` Junio C Hamano
2019-07-19 21:01                 ` Denton Liu
2019-08-25  9:11             ` [PATCH v9 0/9] rebase: learn --keep-base and improvements on fast-forward behaviour Denton Liu
2019-08-25  9:11               ` [PATCH v9 1/9] t3431: add rebase --fork-point tests Denton Liu
2019-08-25  9:12               ` [PATCH v9 2/9] t3432: test rebase fast-forward behavior Denton Liu
2019-08-25  9:12               ` [PATCH v9 3/9] t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests Denton Liu
2019-08-25  9:12               ` [PATCH v9 4/9] t3432: test for --no-ff's interaction with fast-forward Denton Liu
2019-08-25  9:12               ` [PATCH v9 5/9] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-08-25 13:17                 ` Pratyush Yadav
2019-08-26 23:17                   ` Denton Liu
2019-08-25  9:12               ` [PATCH v9 6/9] rebase: fast-forward --onto in more cases Denton Liu
2019-08-25  9:12               ` [PATCH v9 7/9] rebase: fast-forward --fork-point " Denton Liu
2019-08-25  9:12               ` [PATCH v9 8/9] rebase tests: test linear branch topology Denton Liu
2019-08-25  9:12               ` [PATCH v9 9/9] rebase: teach rebase --keep-base Denton Liu
2019-08-25 22:59                 ` Philip Oakley
2019-08-26 19:37               ` [PATCH v9 0/9] rebase: learn --keep-base and improvements on fast-forward behaviour Junio C Hamano
2019-08-27  5:37               ` [PATCH v10 " Denton Liu
2019-08-27  5:37                 ` [PATCH v10 1/9] t3431: add rebase --fork-point tests Denton Liu
2019-08-27  5:37                 ` [PATCH v10 2/9] t3432: test rebase fast-forward behavior Denton Liu
2019-08-27  5:37                 ` [PATCH v10 3/9] t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests Denton Liu
2019-08-27  5:37                 ` [PATCH v10 4/9] t3432: test for --no-ff's interaction with fast-forward Denton Liu
2019-08-27  8:11                   ` SZEDER Gábor
2019-08-27  5:37                 ` [PATCH v10 5/9] rebase: refactor can_fast_forward into goto tower Denton Liu
2019-08-27  5:37                 ` [PATCH v10 6/9] rebase: fast-forward --onto in more cases Denton Liu
2019-08-27  5:38                 ` [PATCH v10 7/9] rebase: fast-forward --fork-point " Denton Liu
2019-08-27  5:38                 ` [PATCH v10 8/9] rebase tests: test linear branch topology Denton Liu
2019-08-27  5:38                 ` [PATCH v10 9/9] rebase: teach rebase --keep-base Denton Liu
2019-05-08  0:12           ` [RFC WIP PATCH v8 01/13] t3431: add rebase --fork-point tests Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 02/13] t3432: test rebase fast-forward behavior Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 03/13] t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 04/13] t3432: test for --no-ff's interaction with fast-forward Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 05/13] rebase: refactor can_fast_forward into goto tower Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` Ævar Arnfjörð Bjarmason [this message]
2019-05-08  0:12           ` [RFC WIP PATCH v8 07/13] rebase: fast-forward --fork-point in more cases Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 08/13] rebase: teach rebase --keep-base Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 09/13] rebase tests: test linear branch topology Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 10/13] rebase: don't rebase linear topology with --fork-point Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 11/13] rebase: eliminate side-effects from can_fast_forward() Ævar Arnfjörð Bjarmason
2019-05-17 21:16             ` Johannes Schindelin
2019-05-08  0:12           ` [RFC WIP PATCH v8 12/13] rebase: add a should_fast_forward() utility function Ævar Arnfjörð Bjarmason
2019-05-08  0:12           ` [RFC WIP PATCH v8 13/13] WIP: can_fast_forward() support for --preserve-merges and --rebase-merges Ævar Arnfjörð Bjarmason
2019-05-17 22:02             ` Johannes Schindelin
2019-04-06 19:44     ` [PATCH v3 0/4] rebase: teach rebase --keep-base Ævar Arnfjörð Bjarmason
2019-04-06 20:38       ` Denton Liu
2019-04-13 21:10         ` Ævar Arnfjörð Bjarmason

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