git/t/t6101-rev-parse-parents.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) 2005 Johannes Schindelin
#
test_description='Test git rev-parse with different parent options'
. ./test-lib.sh
test_cmp_rev_output () {
git rev-parse --verify "$1" >expect &&
eval "$2" >actual &&
test_cmp expect actual
}
test_expect_success 'setup' '
test_commit start &&
test_commit second &&
git checkout --orphan tmp &&
test_commit start2 &&
git checkout master &&
git merge -m next --allow-unrelated-histories start2 &&
test_commit final &&
test_seq 40 |
while read i
do
git checkout --orphan "b$i" &&
test_tick &&
git commit --allow-empty -m "$i" &&
commit=$(git rev-parse --verify HEAD) &&
printf "$commit " >>.git/info/grafts
done
'
test_expect_success 'start is valid' '
git rev-parse start | grep "^[0-9a-f]\{40\}$"
'
test_expect_success 'start^0' '
test_cmp_rev_output tags/start "git rev-parse start^0"
'
test_expect_success 'start^1 not valid' '
test_must_fail git rev-parse --verify start^1
'
test_expect_success 'second^1 = second^' '
test_cmp_rev_output second^ "git rev-parse second^1"
'
test_expect_success 'final^1^1^1' '
test_cmp_rev_output start "git rev-parse final^1^1^1"
'
test_expect_success 'final^1^1^1 = final^^^' '
test_cmp_rev_output final^^^ "git rev-parse final^1^1^1"
'
test_expect_success 'final^1^2' '
test_cmp_rev_output start2 "git rev-parse final^1^2"
'
test_expect_success 'final^1^2 != final^1^1' '
test $(git rev-parse final^1^2) != $(git rev-parse final^1^1)
'
test_expect_success 'final^1^3 not valid' '
test_must_fail git rev-parse --verify final^1^3
'
test_expect_success '--verify start2^1' '
test_must_fail git rev-parse --verify start2^1
'
test_expect_success '--verify start2^0' '
git rev-parse --verify start2^0
'
test_expect_success 'final^1^@ = final^1^1 final^1^2' '
git rev-parse final^1^1 final^1^2 >expect &&
git rev-parse final^1^@ >actual &&
test_cmp expect actual
'
test_expect_success 'final^1^! = final^1 ^final^1^1 ^final^1^2' '
git rev-parse final^1 ^final^1^1 ^final^1^2 >expect &&
git rev-parse final^1^! >actual &&
test_cmp expect actual
'
test_expect_success 'large graft octopus' '
test_cmp_rev_output b31 "git rev-parse --verify b1^30"
'
test_expect_success 'repack for next test' '
git repack -a -d
'
test_expect_success 'short SHA-1 works' '
start=$(git rev-parse --verify start) &&
test_cmp_rev_output start "git rev-parse ${start%?}"
'
test_done