git-commit-vandalism/t/t4068-diff-symmetric.sh
Chris Torek 8bfcb3a690 git diff: improve range handling
When git diff is given a symmetric difference A...B, it chooses
some merge base from the two specified commits (as documented).

This fails, however, if there is *no* merge base: instead, you
see the differences between A and B, which is certainly not what
is expected.

Moreover, if additional revisions are specified on the command
line ("git diff A...B C"), the results get a bit weird:

 * If there is a symmetric difference merge base, this is used
   as the left side of the diff.  The last final ref is used as
   the right side.
 * If there is no merge base, the symmetric status is completely
   lost.  We will produce a combined diff instead.

Similar weirdness occurs if you use, e.g., "git diff C A...B D".
Likewise, using multiple two-dot ranges, or tossing extra
revision specifiers into the command line with two-dot ranges,
or mixing two and three dot ranges, all produce nonsense.

To avoid all this, add a routine to catch the range cases and
verify that that the arguments make sense.  As a side effect,
produce a warning showing *which* merge base is being used when
there are multiple choices; die if there is no merge base.

Signed-off-by: Chris Torek <chris.torek@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-06-12 10:53:44 -07:00

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#!/bin/sh
test_description='behavior of diff with symmetric-diff setups'
. ./test-lib.sh
# build these situations:
# - normal merge with one merge base (br1...b2r);
# - criss-cross merge ie 2 merge bases (br1...master);
# - disjoint subgraph (orphan branch, br3...master).
#
# B---E <-- master
# / \ /
# A X
# \ / \
# C---D--G <-- br1
# \ /
# ---F <-- br2
#
# H <-- br3
#
# We put files into a few commits so that we can verify the
# output as well.
test_expect_success setup '
git commit --allow-empty -m A &&
echo b >b &&
git add b &&
git commit -m B &&
git checkout -b br1 HEAD^ &&
echo c >c &&
git add c &&
git commit -m C &&
git tag commit-C &&
git merge -m D master &&
git tag commit-D &&
git checkout master &&
git merge -m E commit-C &&
git checkout -b br2 commit-C &&
echo f >f &&
git add f &&
git commit -m F &&
git checkout br1 &&
git merge -m G br2 &&
git checkout --orphan br3 &&
git commit -m H
'
test_expect_success 'diff with one merge base' '
git diff commit-D...br1 >tmp &&
tail -n 1 tmp >actual &&
echo +f >expect &&
test_cmp expect actual
'
# The output (in tmp) can have +b or +c depending
# on which merge base (commit B or C) is picked.
# It should have one of those two, which comes out
# to seven lines.
test_expect_success 'diff with two merge bases' '
git diff br1...master >tmp 2>err &&
test_line_count = 7 tmp &&
test_line_count = 1 err
'
test_expect_success 'diff with no merge bases' '
test_must_fail git diff br2...br3 >tmp 2>err &&
test_i18ngrep "fatal: br2...br3: no merge base" err
'
test_expect_success 'diff with too many symmetric differences' '
test_must_fail git diff br1...master br2...br3 >tmp 2>err &&
test_i18ngrep "usage" err
'
test_expect_success 'diff with symmetric difference and extraneous arg' '
test_must_fail git diff master br1...master >tmp 2>err &&
test_i18ngrep "usage" err
'
test_expect_success 'diff with two ranges' '
test_must_fail git diff master br1..master br2..br3 >tmp 2>err &&
test_i18ngrep "usage" err
'
test_expect_success 'diff with ranges and extra arg' '
test_must_fail git diff master br1..master commit-D >tmp 2>err &&
test_i18ngrep "usage" err
'
test_done