Re: [PATCH v5] Add default merge options for all branches

[Junio C Hamano <gitster@pobox.com>]

Junio C Hamano <gitster@pobox.com> writes:

> In any case, your test exposed an ancient breakage ever since the
> per-branch mergeoptions was introduced back when git-merge was a shell
> script (aec7b36 (git-merge: add support for branch.<name>.mergeoptions,
> 2007-09-24).
>
> -- >8 --
> Subject: [PATCH] merge: fix branch.<name>.mergeoptions
> ...

And then on top of that fix, we can do this.

I have a seemingly unrelated change to the existing test but that was
because it only made sure that the --ff-only option made the command fail
when it should fail, without making sure that it does not interfere when
it should succeed.  A typical symptom of "showing off shiny new toy
because I am too excited" developer disease, I would guess.  I didn't want
to forget to fix it.

-- >8 --
Subject: [PATCH] merge: introduce merge.ff configuration variable

This variable gives the default setting for --ff, --no-ff or --ff-only
options of "git merge" command.

Helped-by: Michael Grubb <devel@dailyvoid.com>
Helped-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 * If we were doing the command line option of "merge" from scratch today,
   we probably would have done --ff, --ff=no, and --ff=only, instead of a
   separate --ff-only.  We could still add the latter two as a consistency
   synonyms without deprecating anything, though.

 Documentation/merge-config.txt |   10 +++++++++
 builtin/merge.c                |    9 ++++++++
 t/t7600-merge.sh               |   43 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/Documentation/merge-config.txt b/Documentation/merge-config.txt
index 8920258..861bd6f 100644
--- a/Documentation/merge-config.txt
+++ b/Documentation/merge-config.txt
@@ -16,6 +16,16 @@ merge.defaultToUpstream::
 	to their corresponding remote tracking branches, and the tips of
 	these tracking branches are merged.
 
+merge.ff::
+	By default, git does not create an extra merge commit when merging
+	a commit that is a descendant of the current commit. Instead, the
+	tip of the current branch is fast-forwarded. When set to `false`,
+	this variable tells git to create an extra merge commit in such
+	a case (equivalent to giving the `--no-ff` option from the command
+	line). When set to `only`, only such fast-forward merges are
+	allowed (equivalent to giving the `--ff-only` option from the
+	command line).
+
 merge.log::
 	In addition to branch names, populate the log message with at
 	most the specified number of one-line descriptions from the
diff --git a/builtin/merge.c b/builtin/merge.c
index 4fa789a..1c3ff13 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -550,6 +550,15 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		if (is_bool && shortlog_len)
 			shortlog_len = DEFAULT_MERGE_LOG_LEN;
 		return 0;
+	} else if (!strcmp(k, "merge.ff")) {
+		int boolval = git_config_maybe_bool(k, v);
+		if (0 <= boolval) {
+			allow_fast_forward = boolval;
+		} else if (v && !strcmp(v, "only")) {
+			allow_fast_forward = 1;
+			fast_forward_only = 1;
+		} /* do not barf on values from future versions of git */
+		return 0;
 	} else if (!strcmp(k, "merge.defaulttoupstream")) {
 		default_to_upstream = git_config_bool(k, v);
 		return 0;
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index 5463f87..4f1d4eb 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -225,12 +225,28 @@ test_expect_success 'merge c1 with c2 and c3' '
 
 test_debug 'git log --graph --decorate --oneline --all'
 
-test_expect_success 'failing merges with --ff-only' '
+test_expect_success 'merges with --ff-only' '
 	git reset --hard c1 &&
 	test_tick &&
 	test_must_fail git merge --ff-only c2 &&
 	test_must_fail git merge --ff-only c3 &&
-	test_must_fail git merge --ff-only c2 c3
+	test_must_fail git merge --ff-only c2 c3 &&
+	git reset --hard c0 &&
+	git merge c3 &&
+	verify_head $c3
+'
+
+test_expect_success 'merges with merge.ff=only' '
+	git reset --hard c1 &&
+	test_tick &&
+	test_when_finished "git config --unset merge.ff" &&
+	git config merge.ff only &&
+	test_must_fail git merge c2 &&
+	test_must_fail git merge c3 &&
+	test_must_fail git merge c2 c3 &&
+	git reset --hard c0 &&
+	git merge c3 &&
+	verify_head $c3
 '
 
 test_expect_success 'merge c0 with c1 (no-commit)' '
@@ -447,6 +463,29 @@ test_expect_success 'merge c0 with c1 (no-ff)' '
 
 test_debug 'git log --graph --decorate --oneline --all'
 
+test_expect_success 'merge c0 with c1 (merge.ff=false)' '
+	git reset --hard c0 &&
+	git config merge.ff false &&
+	test_tick &&
+	git merge c1 &&
+	git config --remove-section merge &&
+	verify_merge file result.1 &&
+	verify_parents $c0 $c1
+'
+test_debug 'git log --graph --decorate --oneline --all'
+
+test_expect_success 'combine branch.master.mergeoptions with merge.ff' '
+	git reset --hard c0 &&
+	git config branch.master.mergeoptions --ff
+	git config merge.ff false
+	test_tick &&
+	git merge c1 &&
+	git config --remove-section "branch.master" &&
+	git config --remove-section "merge" &&
+	verify_merge file result.1 &&
+	verify_parents "$c0"
+'
+
 test_expect_success 'combining --squash and --no-ff is refused' '
 	test_must_fail git merge --squash --no-ff c1 &&
 	test_must_fail git merge --no-ff --squash c1
-- 
1.7.5.1.268.gce5bd