git/t/t6026-merge-attr.sh
Junio C Hamano e379fdf34f merge: refuse to create too cool a merge by default
While it makes sense to allow merging unrelated histories of two
projects that started independently into one, in the way "gitk" was
merged to "git" itself aka "the coolest merge ever", such a merge is
still an unusual event.	 Worse, if somebody creates an independent
history by starting from a tarball of an established project and
sends a pull request to the original project, "git merge" however
happily creates such a merge without any sign of something unusual
is happening.

Teach "git merge" to refuse to create such a merge by default,
unless the user passes a new "--allow-unrelated-histories" option to
tell it that the user is aware that two unrelated projects are
merged.

Because such a "two project merge" is a rare event, a configuration
option to always allow such a merge is not added.

We could add the same option to "git pull" and have it passed
through to underlying "git merge".  I do not have a fundamental
opposition against such a feature, but this commit does not do so
and instead leaves it as low-hanging fruit for others, because such
a "two project merge" would be done after fetching the other project
into some location in the working tree of an existing project and
making sure how well they fit together, it is sufficient to allow a
local merge without such an option pass-through from "git pull" to
"git merge".  Many tests that are updated by this patch does the
pass-through manually by turning:

	git pull something

into its equivalent:

	git fetch something &&
	git merge --allow-unrelated-histories FETCH_HEAD

If somebody is inclined to add such an option, updated tests in this
change need to be adjusted back to:

	git pull --allow-unrelated-histories something

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-03-23 12:04:48 -07:00

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#!/bin/sh
#
# Copyright (c) 2007 Junio C Hamano
#
test_description='per path merge controlled by merge attribute'
. ./test-lib.sh
test_expect_success setup '
for f in text binary union
do
echo Initial >$f && git add $f || return 1
done &&
test_tick &&
git commit -m Initial &&
git branch side &&
for f in text binary union
do
echo Master >>$f && git add $f || return 1
done &&
test_tick &&
git commit -m Master &&
git checkout side &&
for f in text binary union
do
echo Side >>$f && git add $f || return 1
done &&
test_tick &&
git commit -m Side &&
git tag anchor
'
test_expect_success merge '
{
echo "binary -merge"
echo "union merge=union"
} >.gitattributes &&
if git merge master
then
echo Gaah, should have conflicted
false
else
echo Ok, conflicted.
fi
'
test_expect_success 'check merge result in index' '
git ls-files -u | grep binary &&
git ls-files -u | grep text &&
! (git ls-files -u | grep union)
'
test_expect_success 'check merge result in working tree' '
git cat-file -p HEAD:binary >binary-orig &&
grep "<<<<<<<" text &&
cmp binary-orig binary &&
! grep "<<<<<<<" union &&
grep Master union &&
grep Side union
'
test_expect_success 'retry the merge with longer context' '
echo text conflict-marker-size=32 >>.gitattributes &&
git checkout -m text &&
sed -ne "/^\([<=>]\)\1\1\1*/{
s/ .*$//
p
}" >actual text &&
grep ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>" actual &&
grep "================================" actual &&
grep "<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<" actual
'
cat >./custom-merge <<\EOF
#!/bin/sh
orig="$1" ours="$2" theirs="$3" exit="$4" path=$5
(
echo "orig is $orig"
echo "ours is $ours"
echo "theirs is $theirs"
echo "path is $path"
echo "=== orig ==="
cat "$orig"
echo "=== ours ==="
cat "$ours"
echo "=== theirs ==="
cat "$theirs"
) >"$ours+"
cat "$ours+" >"$ours"
rm -f "$ours+"
exit "$exit"
EOF
chmod +x ./custom-merge
test_expect_success 'custom merge backend' '
echo "* merge=union" >.gitattributes &&
echo "text merge=custom" >>.gitattributes &&
git reset --hard anchor &&
git config --replace-all \
merge.custom.driver "./custom-merge %O %A %B 0 %P" &&
git config --replace-all \
merge.custom.name "custom merge driver for testing" &&
git merge master &&
cmp binary union &&
sed -e 1,3d text >check-1 &&
o=$(git unpack-file master^:text) &&
a=$(git unpack-file side^:text) &&
b=$(git unpack-file master:text) &&
sh -c "./custom-merge $o $a $b 0 'text'" &&
sed -e 1,3d $a >check-2 &&
cmp check-1 check-2 &&
rm -f $o $a $b
'
test_expect_success 'custom merge backend' '
git reset --hard anchor &&
git config --replace-all \
merge.custom.driver "./custom-merge %O %A %B 1 %P" &&
git config --replace-all \
merge.custom.name "custom merge driver for testing" &&
if git merge master
then
echo "Eh? should have conflicted"
false
else
echo "Ok, conflicted"
fi &&
cmp binary union &&
sed -e 1,3d text >check-1 &&
o=$(git unpack-file master^:text) &&
a=$(git unpack-file anchor:text) &&
b=$(git unpack-file master:text) &&
sh -c "./custom-merge $o $a $b 0 'text'" &&
sed -e 1,3d $a >check-2 &&
cmp check-1 check-2 &&
sed -e 1,3d -e 4q $a >check-3 &&
echo "path is text" >expect &&
cmp expect check-3 &&
rm -f $o $a $b
'
test_expect_success 'up-to-date merge without common ancestor' '
test_create_repo repo1 &&
test_create_repo repo2 &&
test_tick &&
(
cd repo1 &&
>a &&
git add a &&
git commit -m initial
) &&
test_tick &&
(
cd repo2 &&
git commit --allow-empty -m initial
) &&
test_tick &&
(
cd repo1 &&
git fetch ../repo2 master &&
git merge --allow-unrelated-histories FETCH_HEAD
)
'
test_done