Starting at release v1.7.9, if you ask to merge a signed tag, "git merge"
always creates a merge commit, even when the tag points at a commit that
happens to be a descendant of your current commit.
Unfortunately, this interacts rather badly for people who use --ff-only to
make sure that their branch is free of local developments. It used to be
possible to say:
$ git checkout -b frotz v1.7.9~30
$ git merge --ff-only v1.7.9
and expect that the resulting tip of frotz branch matches v1.7.9^0 (aka
the commit tagged as v1.7.9), but this fails with the updated Git with:
fatal: Not possible to fast-forward, aborting.
because a merge that merges v1.7.9 tag to v1.7.9~30 cannot be created by
fast forwarding.
We could teach users that now they have to do
$ git merge --ff-only v1.7.9^0
but it is far more pleasant for users if we DWIMmed this ourselves.
When an integrator pulls in a topic from a lieutenant via a signed tag,
even when the work done by the lieutenant happens to fast-forward, the
integrator wants to have a merge record, so the integrator will not be
asking for --ff-only when running "git pull" in such a case. Therefore,
this change should not regress the support for the use case v1.7.9 wanted
to add.
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
Junio C Hamano <gitster@xxxxxxxxx> writes:
We could solve this in one of two ways. We could tell them to merge
v3.2.3^0 instead. Or we could just go ahead and do that for them
automatically ourselves. I am inclined to say that we should unwrap
the tag given from the command line when --ff-only was given, i.e. we
do the latter.
And it turns out that it is just a single-liner patch.
builtin/merge.c | 3 ++-
t/t7600-merge.sh | 13 +++++++++++++
2 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/builtin/merge.c b/builtin/merge.c
index 3a45172..b4fbc60 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1283,7 +1283,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
sha1_to_hex(commit->object.sha1));
setenv(buf.buf, argv[i], 1);
strbuf_reset(&buf);
- if (merge_remote_util(commit) &&
+ if (!fast_forward_only &&
+ merge_remote_util(commit) &&
merge_remote_util(commit)->obj &&
merge_remote_util(commit)->obj->type == OBJ_TAG) {
option_edit = 1;
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index 5d8c428..a598dfa 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -27,6 +27,7 @@ Testing basic merge operations/option parsing.
'
. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-gpg.sh
printf '%s\n' 1 2 3 4 5 6 7 8 9 >file
printf '%s\n' '1 X' 2 3 4 5 6 7 8 9 >file.1
@@ -670,4 +671,16 @@ test_expect_success 'merge --no-ff --edit' '
test_cmp actual expected
'
+test_expect_success GPG 'merge --ff-only tag' '
+ git reset --hard c0 &&
+ git commit --allow-empty -m "A newer commit" &&
+ git tag -s -m "A newer commit" signed &&
+ git reset --hard c0 &&
+
+ git merge --ff-only signed &&
+ git rev-parse signed^0 >expect &&
+ git rev-parse HEAD >actual &&
+ test_cmp actual expect
+'
+
test_done
--
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