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From: Alban Gruin <alban.gruin@gmail.com>
To: git@vger.kernel.org
Cc: Junio C Hamano <gitster@pobox.com>,
	Phillip Wood <phillip.wood123@gmail.com>,
	Alban Gruin <alban.gruin@gmail.com>
Subject: [PATCH v6 02/13] t6060: modify multiple files to expose a possible issue with merge-index
Date: Tue, 24 Nov 2020 12:53:04 +0100	[thread overview]
Message-ID: <20201124115315.13311-3-alban.gruin@gmail.com> (raw)
In-Reply-To: <20201124115315.13311-1-alban.gruin@gmail.com>

Currently, merge-index iterates over every index entry, skipping stage0
entries.  It will then count how many entries following the current one
have the same name, then fork to do the merge.  It will then increase
the iterator by the number of entries to skip them.  This behaviour is
correct, as even if the subprocess modifies the index, merge-index does
not reload it at all.

But when it will be rewritten to use a function, the index it will use
will be modified and may shrink when a conflict happens or if a file is
removed, so we have to be careful to handle such cases.

Here is an example:

 *    Merge branches, file1 and file2 are trivially mergeable.
 |\
 | *  Modifies file1 and file2.
 * |  Modifies file1 and file2.
 |/
 *    Adds file1 and file2.

When the merge happens, the index will look like that:

 i -> 0. file1 (stage1)
      1. file1 (stage2)
      2. file1 (stage3)
      3. file2 (stage1)
      4. file2 (stage2)
      5. file2 (stage3)

merge-index handles `file1' first.  As it appears 3 times after the
iterator, it is merged.  The index is now stale, `i' is increased by 3,
and the index now looks like this:

      0. file1 (stage1)
      1. file1 (stage2)
      2. file1 (stage3)
 i -> 3. file2 (stage1)
      4. file2 (stage2)
      5. file2 (stage3)

`file2' appears three times too, so it is merged.

With a naive rewrite, the index would look like this:

      0. file1 (stage0)
      1. file2 (stage1)
      2. file2 (stage2)
 i -> 3. file2 (stage3)

`file2' appears once at the iterator or after, so it will be added,
_not_ merged.  Which is wrong.

A naive rewrite would lead to unproperly merged files, or even files not
handled at all.

This changes t6060 to reproduce this case, by creating 2 files instead
of 1, to check the correctness of the soon-to-be-rewritten merge-index.
The files are identical, which is not really important -- the factors
that could trigger this issue are that they should be separated by at
most one entry in the index, and that the first one in the index should
be trivially mergeable.

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
---
 t/t6060-merge-index.sh | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/t/t6060-merge-index.sh b/t/t6060-merge-index.sh
index ddf34f0115..9e15ceb957 100755
--- a/t/t6060-merge-index.sh
+++ b/t/t6060-merge-index.sh
@@ -7,16 +7,19 @@ test_expect_success 'setup diverging branches' '
 	for i in 1 2 3 4 5 6 7 8 9 10; do
 		echo $i
 	done >file &&
-	git add file &&
+	cp file file2 &&
+	git add file file2 &&
 	git commit -m base &&
 	git tag base &&
 	sed s/2/two/ <file >tmp &&
 	mv tmp file &&
+	cp file file2 &&
 	git commit -a -m two &&
 	git tag two &&
 	git checkout -b other HEAD^ &&
 	sed s/10/ten/ <file >tmp &&
 	mv tmp file &&
+	cp file file2 &&
 	git commit -a -m ten &&
 	git tag ten
 '
@@ -35,8 +38,11 @@ ten
 EOF
 
 test_expect_success 'read-tree does not resolve content merge' '
+	cat >expect <<-\EOF &&
+	file
+	file2
+	EOF
 	git read-tree -i -m base ten two &&
-	echo file >expect &&
 	git diff-files --name-only --diff-filter=U >unmerged &&
 	test_cmp expect unmerged
 '
-- 
2.29.2.260.ge31aba42fb


  parent reply	other threads:[~2020-11-24 11:56 UTC|newest]

Thread overview: 183+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-25 12:19 [RFC PATCH v1 00/17] Rewrite the remaining merge strategies from shell to C Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 01/17] t6027: modernise tests Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 02/17] merge-one-file: rewrite in C Alban Gruin
2020-06-25 14:55   ` Chris Torek
2020-06-25 15:16   ` Phillip Wood
2020-06-25 18:17     ` Phillip Wood
2020-06-26 14:33       ` Phillip Wood
2020-07-12 11:22     ` Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 03/17] merge-one-file: remove calls to external processes Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 04/17] merge-one-file: use error() instead of fprintf(stderr, ...) Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 05/17] merge-one-file: libify merge_one_file() Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 06/17] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2020-06-26 10:13   ` Phillip Wood
2020-06-26 14:32     ` Phillip Wood
2020-07-12 11:36     ` Alban Gruin
2020-07-12 18:02       ` Phillip Wood
2020-07-12 20:10         ` Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 07/17] merge-resolve: rewrite in C Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 08/17] merge-resolve: remove calls to external processes Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 09/17] merge-resolve: libify merge_resolve() Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 10/17] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 11/17] merge-octopus: rewrite in C Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 12/17] merge-octopus: remove calls to external processes Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 13/17] merge-octopus: libify merge_octopus() Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 14/17] merge: use the "resolve" strategy without forking Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 15/17] merge: use the "octopus" " Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 16/17] sequencer: use the "resolve" " Alban Gruin
2020-06-25 16:11   ` Phillip Wood
2020-07-12 11:27     ` Alban Gruin
2020-06-25 12:19 ` [RFC PATCH v1 17/17] sequencer: use the "octopus" merge " Alban Gruin
2020-09-01 10:56 ` [PATCH v2 00/11] Rewrite the remaining merge strategies from shell to C Alban Gruin
2020-09-01 10:56   ` [PATCH v2 01/11] t6027: modernise tests Alban Gruin
2020-09-01 10:56   ` [PATCH v2 02/11] merge-one-file: rewrite in C Alban Gruin
2020-09-01 21:06     ` Junio C Hamano
2020-09-02 14:50       ` Alban Gruin
2020-09-01 10:56   ` [PATCH v2 03/11] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2020-09-01 21:11     ` Junio C Hamano
2020-09-02 15:37       ` Alban Gruin
2020-09-01 10:56   ` [PATCH v2 04/11] merge-index: don't fork if the requested program is `git-merge-one-file' Alban Gruin
2020-09-01 10:56   ` [PATCH v2 05/11] merge-resolve: rewrite in C Alban Gruin
2020-09-01 10:57   ` [PATCH v2 06/11] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2020-09-01 10:57   ` [PATCH v2 07/11] merge-octopus: rewrite in C Alban Gruin
2020-09-01 10:57   ` [PATCH v2 08/11] merge: use the "resolve" strategy without forking Alban Gruin
2020-09-01 10:57   ` [PATCH v2 09/11] merge: use the "octopus" " Alban Gruin
2020-09-01 10:57   ` [PATCH v2 10/11] sequencer: use the "resolve" " Alban Gruin
2020-09-01 10:57   ` [PATCH v2 11/11] sequencer: use the "octopus" merge " Alban Gruin
2020-10-05 12:26   ` [PATCH v3 00/11] Rewrite the remaining merge strategies from shell to C Alban Gruin
2020-10-05 12:26     ` [PATCH v3 01/11] t6027: modernise tests Alban Gruin
2020-10-06 20:50       ` Junio C Hamano
2020-10-05 12:26     ` [PATCH v3 02/11] merge-one-file: rewrite in C Alban Gruin
2020-10-06 22:01       ` Junio C Hamano
2020-10-21 19:47         ` Alban Gruin
2020-10-21 20:28           ` Junio C Hamano
2020-10-21 21:20             ` Junio C Hamano
2020-10-21 20:30           ` Junio C Hamano
2020-10-05 12:26     ` [PATCH v3 03/11] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2020-10-09  4:48       ` Junio C Hamano
2020-11-06 19:53         ` Alban Gruin
2020-10-05 12:26     ` [PATCH v3 04/11] merge-index: don't fork if the requested program is `git-merge-one-file' Alban Gruin
2020-10-16 19:07       ` Junio C Hamano
2020-10-05 12:26     ` [PATCH v3 05/11] merge-resolve: rewrite in C Alban Gruin
2020-10-16 19:19       ` Junio C Hamano
2020-11-06 19:53         ` Alban Gruin
2020-10-05 12:26     ` [PATCH v3 06/11] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2020-10-05 12:26     ` [PATCH v3 07/11] merge-octopus: rewrite in C Alban Gruin
2020-10-05 12:26     ` [PATCH v3 08/11] merge: use the "resolve" strategy without forking Alban Gruin
2020-10-05 12:26     ` [PATCH v3 09/11] merge: use the "octopus" " Alban Gruin
2020-10-05 12:26     ` [PATCH v3 10/11] sequencer: use the "resolve" " Alban Gruin
2020-10-05 12:26     ` [PATCH v3 11/11] sequencer: use the "octopus" merge " Alban Gruin
2020-10-07  6:57     ` [PATCH v3 00/11] Rewrite the remaining merge strategies from shell to C Johannes Schindelin
2020-11-13 11:04     ` [PATCH v4 00/12] " Alban Gruin
2020-11-13 11:04       ` [PATCH v4 01/12] t6027: modernise tests Alban Gruin
2020-11-13 11:04       ` [PATCH v4 02/12] update-index: move add_cacheinfo() to read-cache.c Alban Gruin
2020-11-13 11:04       ` [PATCH v4 03/12] merge-one-file: rewrite in C Alban Gruin
2020-11-13 11:04       ` [PATCH v4 04/12] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2020-11-13 11:04       ` [PATCH v4 05/12] merge-index: don't fork if the requested program is `git-merge-one-file' Alban Gruin
2020-11-13 11:04       ` [PATCH v4 06/12] merge-resolve: rewrite in C Alban Gruin
2020-11-13 11:04       ` [PATCH v4 07/12] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2020-11-13 11:04       ` [PATCH v4 08/12] merge-octopus: rewrite in C Alban Gruin
2020-11-13 11:04       ` [PATCH v4 09/12] merge: use the "resolve" strategy without forking Alban Gruin
2020-11-13 11:04       ` [PATCH v4 10/12] merge: use the "octopus" " Alban Gruin
2020-11-13 11:04       ` [PATCH v4 11/12] sequencer: use the "resolve" " Alban Gruin
2020-11-13 11:04       ` [PATCH v4 12/12] sequencer: use the "octopus" merge " Alban Gruin
2020-11-16 10:21       ` [PATCH v5 00/12] Rewrite the remaining merge strategies from shell to C Alban Gruin
2020-11-16 10:21         ` [PATCH v5 01/12] t6027: modernise tests Alban Gruin
2020-11-16 10:21         ` [PATCH v5 02/12] update-index: move add_cacheinfo() to read-cache.c Alban Gruin
2020-11-16 10:21         ` [PATCH v5 03/12] merge-one-file: rewrite in C Alban Gruin
2020-11-16 10:21         ` [PATCH v5 04/12] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2020-11-16 10:21         ` [PATCH v5 05/12] merge-index: don't fork if the requested program is `git-merge-one-file' Alban Gruin
2020-11-16 10:21         ` [PATCH v5 06/12] merge-resolve: rewrite in C Alban Gruin
2020-11-16 10:21         ` [PATCH v5 07/12] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2020-11-16 10:21         ` [PATCH v5 08/12] merge-octopus: rewrite in C Alban Gruin
2020-11-16 10:21         ` [PATCH v5 09/12] merge: use the "resolve" strategy without forking Alban Gruin
2020-11-16 10:21         ` [PATCH v5 10/12] merge: use the "octopus" " Alban Gruin
2020-11-16 10:21         ` [PATCH v5 11/12] sequencer: use the "resolve" " Alban Gruin
2020-11-16 10:21         ` [PATCH v5 12/12] sequencer: use the "octopus" merge " Alban Gruin
2020-11-24 11:53         ` [PATCH v6 00/13] Rewrite the remaining merge strategies from shell to C Alban Gruin
2020-11-24 11:53           ` [PATCH v6 01/13] t6407: modernise tests Alban Gruin
2020-11-24 11:53           ` Alban Gruin [this message]
2020-11-24 11:53           ` [PATCH v6 03/13] update-index: move add_cacheinfo() to read-cache.c Alban Gruin
2020-12-22 20:54             ` Junio C Hamano
2020-11-24 11:53           ` [PATCH v6 04/13] merge-one-file: rewrite in C Alban Gruin
2020-12-22 21:36             ` Junio C Hamano
2021-01-03 22:41               ` Alban Gruin
2021-01-08  6:54                 ` Junio C Hamano
2020-11-24 11:53           ` [PATCH v6 05/13] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2021-01-05 15:59             ` Derrick Stolee
2021-01-05 23:20               ` Alban Gruin
2020-11-24 11:53           ` [PATCH v6 06/13] merge-index: don't fork if the requested program is `git-merge-one-file' Alban Gruin
2021-01-05 16:11             ` Derrick Stolee
2021-01-05 17:35               ` Martin Ågren
2021-01-05 23:20                 ` Alban Gruin
2021-01-05 23:20               ` Alban Gruin
2021-01-06  2:04                 ` Junio C Hamano
2021-01-10 17:15                   ` Alban Gruin
2021-01-10 20:51                     ` Junio C Hamano
2021-03-08 20:32                       ` Alban Gruin
2020-11-24 11:53           ` [PATCH v6 07/13] merge-resolve: rewrite in C Alban Gruin
2020-11-24 11:53           ` [PATCH v6 08/13] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2021-01-05 16:19             ` Derrick Stolee
2020-11-24 11:53           ` [PATCH v6 09/13] merge-octopus: rewrite in C Alban Gruin
2021-01-05 16:40             ` Derrick Stolee
2020-11-24 11:53           ` [PATCH v6 10/13] merge: use the "resolve" strategy without forking Alban Gruin
2021-01-05 16:45             ` Derrick Stolee
2020-11-24 11:53           ` [PATCH v6 11/13] merge: use the "octopus" " Alban Gruin
2020-11-24 11:53           ` [PATCH v6 12/13] sequencer: use the "resolve" " Alban Gruin
2020-11-24 11:53           ` [PATCH v6 13/13] sequencer: use the "octopus" merge " Alban Gruin
2020-11-24 19:34           ` [PATCH v6 00/13] Rewrite the remaining merge strategies from shell to C SZEDER Gábor
2021-01-05 16:50           ` Derrick Stolee
2021-03-17 20:49           ` [PATCH v7 00/15] " Alban Gruin
2021-03-17 20:49             ` [PATCH v7 01/15] t6407: modernise tests Alban Gruin
2021-03-17 20:49             ` [PATCH v7 02/15] t6060: modify multiple files to expose a possible issue with merge-index Alban Gruin
2021-03-17 20:49             ` [PATCH v7 03/15] t6060: add tests for removed files Alban Gruin
2021-03-22 21:36               ` Johannes Schindelin
2021-03-23 20:43                 ` Alban Gruin
2021-03-17 20:49             ` [PATCH v7 04/15] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2021-03-17 20:49             ` [PATCH v7 05/15] merge-index: drop the index Alban Gruin
2021-03-17 20:49             ` [PATCH v7 06/15] merge-index: add a new way to invoke `git-merge-one-file' Alban Gruin
2021-03-17 20:49             ` [PATCH v7 07/15] update-index: move add_cacheinfo() to read-cache.c Alban Gruin
2021-03-22 21:59               ` Johannes Schindelin
2021-03-23 20:45                 ` Alban Gruin
2021-03-17 20:49             ` [PATCH v7 08/15] merge-one-file: rewrite in C Alban Gruin
2021-03-22 22:20               ` Johannes Schindelin
2021-03-23 20:53                 ` Alban Gruin
2021-03-24  9:10                   ` Johannes Schindelin
2021-04-10 14:17                     ` Alban Gruin
2021-03-17 20:49             ` [PATCH v7 09/15] merge-resolve: " Alban Gruin
2021-03-23 22:21               ` Johannes Schindelin
2021-04-10 14:17                 ` Alban Gruin
2021-03-17 20:49             ` [PATCH v7 10/15] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2021-03-17 20:49             ` [PATCH v7 11/15] merge-octopus: rewrite in C Alban Gruin
2021-03-23 23:58               ` Johannes Schindelin
2021-03-17 20:49             ` [PATCH v7 12/15] merge: use the "resolve" strategy without forking Alban Gruin
2021-03-17 20:49             ` [PATCH v7 13/15] merge: use the "octopus" " Alban Gruin
2021-03-17 20:49             ` [PATCH v7 14/15] sequencer: use the "resolve" " Alban Gruin
2021-03-17 20:49             ` [PATCH v7 15/15] sequencer: use the "octopus" merge " Alban Gruin
2022-08-09 18:54             ` [PATCH v8 00/14] Rewrite the remaining merge strategies from shell to C Alban Gruin
2022-08-09 18:54               ` [PATCH v8 01/14] t6060: modify multiple files to expose a possible issue with merge-index Alban Gruin
2022-08-09 18:54               ` [PATCH v8 02/14] t6060: add tests for removed files Alban Gruin
2022-08-09 18:54               ` [PATCH v8 03/14] merge-index: libify merge_one_path() and merge_all() Alban Gruin
2022-08-17  2:10                 ` Ævar Arnfjörð Bjarmason
2022-08-09 18:54               ` [PATCH v8 04/14] merge-index: drop the index Alban Gruin
2022-08-09 18:54               ` [PATCH v8 05/14] merge-index: add a new way to invoke `git-merge-one-file' Alban Gruin
2022-08-09 21:36                 ` Johannes Schindelin
2022-08-10 13:14                   ` Phillip Wood
2022-08-09 18:54               ` [PATCH v8 06/14] update-index: move add_cacheinfo() to read-cache.c Alban Gruin
2022-08-09 18:54               ` [PATCH v8 07/14] merge-one-file: rewrite in C Alban Gruin
2022-08-09 22:01                 ` Johannes Schindelin
2022-08-09 18:54               ` [PATCH v8 08/14] merge-resolve: " Alban Gruin
2022-08-10 15:03                 ` Phillip Wood
2022-08-10 21:20                   ` Junio C Hamano
2022-08-16 12:09                     ` Johannes Schindelin
2022-08-16 19:36                       ` Junio C Hamano
2022-08-16 12:17                   ` Johannes Schindelin
2022-08-16 14:02                     ` Phillip Wood
2022-08-17  2:16                 ` Ævar Arnfjörð Bjarmason
2022-08-09 18:54               ` [PATCH v8 09/14] merge-recursive: move better_branch_name() to merge.c Alban Gruin
2022-08-09 18:54               ` [PATCH v8 10/14] merge-octopus: rewrite in C Alban Gruin
2022-08-09 18:54               ` [PATCH v8 11/14] merge: use the "resolve" strategy without forking Alban Gruin
2022-08-13 16:18                 ` Junio C Hamano
2022-08-09 18:54               ` [PATCH v8 12/14] merge: use the "octopus" " Alban Gruin
2022-08-09 18:54               ` [PATCH v8 13/14] sequencer: use the "resolve" " Alban Gruin
2022-08-09 18:54               ` [PATCH v8 14/14] sequencer: use the "octopus" " Alban Gruin

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