git-commit-vandalism/t/t6427-diff3-conflict-markers.sh
Phillip Wood 4496526f80 xdiff: implement a zealous diff3, or "zdiff3"
"zdiff3" is identical to ordinary diff3 except that it allows compaction
of common lines on the two sides of history at the beginning or end of
the conflict hunk.  For example, the following diff3 conflict:

    1
    2
    3
    4
    <<<<<<
    A
    B
    C
    D
    E
    ||||||
    5
    6
    ======
    A
    X
    C
    Y
    E
    >>>>>>
    7
    8
    9

has common lines 'A', 'C', and 'E' on the two sides.  With zdiff3, one
would instead get the following conflict:

    1
    2
    3
    4
    A
    <<<<<<
    B
    C
    D
    ||||||
    5
    6
    ======
    X
    C
    Y
    >>>>>>
    E
    7
    8
    9

Note that the common lines, 'A', and 'E' were moved outside the
conflict.  Unlike with the two-way conflicts from the 'merge'
conflictStyle, the zdiff3 conflict is NOT split into multiple conflict
regions to allow the common 'C' lines to be shown outside a conflict,
because zdiff3 shows the base version too and the base version cannot be
reasonably split.

Note also that the removing of lines common to the two sides might make
the remaining text inside the conflict region match the base text inside
the conflict region (for example, if the diff3 conflict had '5 6 E' on
the right side of the conflict, then the common line 'E' would be moved
outside and both the base and right side's remaining conflict text would
be the lines '5' and '6').  This has the potential to surprise users and
make them think there should not have been a conflict, but there
definitely was a conflict and it should remain.

Based-on-patch-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Co-authored-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-12-01 14:45:58 -08:00

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#!/bin/sh
test_description='recursive merge diff3 style conflict markers'
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
. ./test-lib.sh
# Setup:
# L1
# \
# ?
# /
# R1
#
# Where:
# L1 and R1 both have a file named 'content' but have no common history
#
test_expect_success 'setup no merge base' '
test_create_repo no_merge_base &&
(
cd no_merge_base &&
git checkout -b L &&
test_commit A content A &&
git checkout --orphan R &&
test_commit B content B
)
'
test_expect_success 'check no merge base' '
(
cd no_merge_base &&
git checkout L^0 &&
test_must_fail git -c merge.conflictstyle=diff3 merge --allow-unrelated-histories -s recursive R^0 &&
grep "|||||| empty tree" content
)
'
# Setup:
# L1
# / \
# main ?
# \ /
# R1
#
# Where:
# L1 and R1 have modified the same file ('content') in conflicting ways
#
test_expect_success 'setup unique merge base' '
test_create_repo unique_merge_base &&
(
cd unique_merge_base &&
test_commit base content "1
2
3
4
5
" &&
git branch L &&
git branch R &&
git checkout L &&
test_commit L content "1
2
3
4
5
7" &&
git checkout R &&
git rm content &&
test_commit R renamed "1
2
3
4
5
six"
)
'
test_expect_success 'check unique merge base' '
(
cd unique_merge_base &&
git checkout L^0 &&
MAIN=$(git rev-parse --short main) &&
test_must_fail git -c merge.conflictstyle=diff3 merge -s recursive R^0 &&
grep "|||||| $MAIN:content" renamed
)
'
# Setup:
# L1---L2--L3
# / \ / \
# main X1 ?
# \ / \ /
# R1---R2--R3
#
# Where:
# commits L1 and R1 have modified the same file in non-conflicting ways
# X1 is an auto-generated merge-base used when merging L1 and R1
# commits L2 and R2 are merges of R1 and L1 into L1 and R1, respectively
# commits L3 and R3 both modify 'content' in conflicting ways
#
test_expect_success 'setup multiple merge bases' '
test_create_repo multiple_merge_bases &&
(
cd multiple_merge_bases &&
test_commit initial content "1
2
3
4
5" &&
git branch L &&
git branch R &&
# Create L1
git checkout L &&
test_commit L1 content "0
1
2
3
4
5" &&
# Create R1
git checkout R &&
test_commit R1 content "1
2
3
4
5
6" &&
# Create L2
git checkout L &&
git merge R1 &&
# Create R2
git checkout R &&
git merge L1 &&
# Create L3
git checkout L &&
test_commit L3 content "0
1
2
3
4
5
A" &&
# Create R3
git checkout R &&
git rm content &&
test_commit R3 renamed "0
2
3
4
5
six"
)
'
test_expect_success 'check multiple merge bases' '
(
cd multiple_merge_bases &&
git checkout L^0 &&
test_must_fail git -c merge.conflictstyle=diff3 merge -s recursive R^0 &&
grep "|||||| merged common ancestors:content" renamed
)
'
test_expect_success 'rebase --merge describes parent of commit being picked' '
test_create_repo rebase &&
(
cd rebase &&
test_commit base file &&
test_commit main file &&
git checkout -b side HEAD^ &&
test_commit side file &&
test_must_fail git -c merge.conflictstyle=diff3 rebase --merge main &&
grep "||||||| parent of" file
)
'
test_expect_success 'rebase --apply describes fake ancestor base' '
(
cd rebase &&
git rebase --abort &&
test_must_fail git -c merge.conflictstyle=diff3 rebase --apply main &&
grep "||||||| constructed merge base" file
)
'
test_setup_zdiff3 () {
test_create_repo zdiff3 &&
(
cd zdiff3 &&
test_write_lines 1 2 3 4 5 6 7 8 9 >basic &&
test_write_lines 1 2 3 AA 4 5 BB 6 7 8 >middle-common &&
test_write_lines 1 2 3 4 5 6 7 8 9 >interesting &&
test_write_lines 1 2 3 4 5 6 7 8 9 >evil &&
git add basic middle-common interesting evil &&
git commit -m base &&
git branch left &&
git branch right &&
git checkout left &&
test_write_lines 1 2 3 4 A B C D E 7 8 9 >basic &&
test_write_lines 1 2 3 CC 4 5 DD 6 7 8 >middle-common &&
test_write_lines 1 2 3 4 A B C D E F G H I J 7 8 9 >interesting &&
test_write_lines 1 2 3 4 X A B C 7 8 9 >evil &&
git add -u &&
git commit -m letters &&
git checkout right &&
test_write_lines 1 2 3 4 A X C Y E 7 8 9 >basic &&
test_write_lines 1 2 3 EE 4 5 FF 6 7 8 >middle-common &&
test_write_lines 1 2 3 4 A B C 5 6 G H I J 7 8 9 >interesting &&
test_write_lines 1 2 3 4 Y A B C B C 7 8 9 >evil &&
git add -u &&
git commit -m permuted
)
}
test_expect_success 'check zdiff3 markers' '
test_setup_zdiff3 &&
(
cd zdiff3 &&
git checkout left^0 &&
base=$(git rev-parse --short HEAD^1) &&
test_must_fail git -c merge.conflictstyle=zdiff3 merge -s recursive right^0 &&
test_write_lines 1 2 3 4 A \
"<<<<<<< HEAD" B C D \
"||||||| $base" 5 6 \
======= X C Y \
">>>>>>> right^0" \
E 7 8 9 \
>expect &&
test_cmp expect basic &&
test_write_lines 1 2 3 \
"<<<<<<< HEAD" CC \
"||||||| $base" AA \
======= EE \
">>>>>>> right^0" \
4 5 \
"<<<<<<< HEAD" DD \
"||||||| $base" BB \
======= FF \
">>>>>>> right^0" \
6 7 8 \
>expect &&
test_cmp expect middle-common &&
test_write_lines 1 2 3 4 A B C \
"<<<<<<< HEAD" D E F \
"||||||| $base" 5 6 \
======= 5 6 \
">>>>>>> right^0" \
G H I J 7 8 9 \
>expect &&
test_cmp expect interesting &&
# Not passing this one yet; the common "B C" lines is still
# being left in the conflict blocks on the left and right
# sides.
test_write_lines 1 2 3 4 \
"<<<<<<< HEAD" X A \
"||||||| $base" 5 6 \
======= Y A B C \
">>>>>>> right^0" \
B C 7 8 9 \
>expect &&
test_cmp expect evil
)
'
test_done