"Chris Torek via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes: > From: Chris Torek <chris.torek@xxxxxxxxx> > > According to the documentation, "git diff" takes at most two commit-ish, > or an A..B style range, or an A...B style symmetric difference range. > The autosquash-and-exec test relied on "git diff HEAD^!", which works > fine for ordinary commits as the revision parse produces two commit-ish, > namely ^HEAD^ and HEAD. > > For merge commits, however, this test makes use of an undocumented > feature: s/undocumented feature/undefined behaviour/; The show.sh scripts wants to compute the diff against first parent, and it uses a range notation HEAD^! which happens to mean HEAD^..HEAD for a single parent commit, but it forgets that the commit it may get fed could be a merge. What the code happens to do when given "git diff ^HEAD^2 HEAD^..HEAD" is undefined behaviour and does not even ... > the resulting revision parse has all the parents as UNINTERESTING > followed by the HEAD commit. This looks identical to a symmetric > diff parse, which lists the merge bases as UNINTERESTING, followed by > the A (UNINTERESTING) and B revs. So the diff winds up treating it > as one, using the first oid (i.e., HEAD^) and the last (i.e., HEAD). > The documentation, however, says nothing about this usage. ...deserve to be explained in a paragraph like this, I would think. > Since diff actually just uses HEAD^ and HEAD, call for these directly > here. That makes it possible to improve the diff code's handling of > symmetric difference arguments. Yes, the resulting code expresses the intent much better. > > Signed-off-by: Chris Torek <chris.torek@xxxxxxxxx> > --- > t/t3430-rebase-merges.sh | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh > index a1bc3e20016..b454f400ebd 100755 > --- a/t/t3430-rebase-merges.sh > +++ b/t/t3430-rebase-merges.sh > @@ -420,7 +420,7 @@ test_expect_success 'with --autosquash and --exec' ' > git commit --fixup B B.t && > write_script show.sh <<-\EOF && > subject="$(git show -s --format=%s HEAD)" > - content="$(git diff HEAD^! | tail -n 1)" > + content="$(git diff HEAD^ HEAD | tail -n 1)" > echo "$subject: $content" > EOF > test_tick &&
