git/t/t6009-rev-list-parent.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
test_description='ancestor culling and limiting by parent number'
. ./test-lib.sh
check_revlist () {
rev_list_args="$1" &&
shift &&
git rev-parse "$@" >expect &&
git rev-list $rev_list_args --all >actual &&
test_cmp expect actual
}
test_expect_success setup '
touch file &&
git add file &&
test_commit one &&
test_tick=$(($test_tick - 2400)) &&
test_commit two &&
test_commit three &&
test_commit four &&
git log --pretty=oneline --abbrev-commit
'
test_expect_success 'one is ancestor of others and should not be shown' '
git rev-list one --not four >result &&
>expect &&
test_cmp expect result
'
test_expect_success 'setup roots, merges and octopuses' '
git checkout --orphan newroot &&
test_commit five &&
git checkout -b sidebranch two &&
test_commit six &&
git checkout -b anotherbranch three &&
test_commit seven &&
git checkout -b yetanotherbranch four &&
test_commit eight &&
git checkout master &&
test_tick &&
git merge --allow-unrelated-histories -m normalmerge newroot &&
git tag normalmerge &&
test_tick &&
git merge -m tripus sidebranch anotherbranch &&
git tag tripus &&
git checkout -b tetrabranch normalmerge &&
test_tick &&
git merge -m tetrapus sidebranch anotherbranch yetanotherbranch &&
git tag tetrapus &&
git checkout master
'
test_expect_success 'rev-list roots' '
check_revlist "--max-parents=0" one five
'
test_expect_success 'rev-list no merges' '
check_revlist "--max-parents=1" one eight seven six five four three two &&
check_revlist "--no-merges" one eight seven six five four three two
'
test_expect_success 'rev-list no octopuses' '
check_revlist "--max-parents=2" one normalmerge eight seven six five four three two
'
test_expect_success 'rev-list no roots' '
check_revlist "--min-parents=1" tetrapus tripus normalmerge eight seven six four three two
'
test_expect_success 'rev-list merges' '
check_revlist "--min-parents=2" tetrapus tripus normalmerge &&
check_revlist "--merges" tetrapus tripus normalmerge
'
test_expect_success 'rev-list octopus' '
check_revlist "--min-parents=3" tetrapus tripus
'
test_expect_success 'rev-list ordinary commits' '
check_revlist "--min-parents=1 --max-parents=1" eight seven six four three two
'
test_expect_success 'rev-list --merges --no-merges yields empty set' '
check_revlist "--min-parents=2 --no-merges" &&
check_revlist "--merges --no-merges" &&
check_revlist "--no-merges --merges"
'
test_expect_success 'rev-list override and infinities' '
check_revlist "--min-parents=2 --max-parents=1 --max-parents=3" tripus normalmerge &&
check_revlist "--min-parents=1 --min-parents=2 --max-parents=7" tetrapus tripus normalmerge &&
check_revlist "--min-parents=2 --max-parents=8" tetrapus tripus normalmerge &&
check_revlist "--min-parents=2 --max-parents=-1" tetrapus tripus normalmerge &&
check_revlist "--min-parents=2 --no-max-parents" tetrapus tripus normalmerge &&
check_revlist "--max-parents=0 --min-parents=1 --no-min-parents" one five
'
test_expect_success 'dodecapus' '
roots= &&
for i in 1 2 3 4 5 6 7 8 9 10 11
do
git checkout -b root$i five &&
test_commit $i &&
roots="$roots root$i" ||
return
done &&
git checkout master &&
test_tick &&
git merge -m dodecapus $roots &&
git tag dodecapus &&
check_revlist "--min-parents=4" dodecapus tetrapus &&
check_revlist "--min-parents=8" dodecapus &&
check_revlist "--min-parents=12" dodecapus &&
check_revlist "--min-parents=13" &&
check_revlist "--min-parents=4 --max-parents=11" tetrapus
'
test_expect_success 'ancestors with the same commit time' '
test_tick_keep=$test_tick &&
for i in 1 2 3 4 5 6 7 8; do
test_tick=$test_tick_keep
test_commit t$i
done &&
git rev-list t1^! --not t$i >result &&
>expect &&
test_cmp expect result
'
test_done