Re: [PATCH 1/2] sequencer: unify label lookup

[Phillip Wood <phillip.wood123@xxxxxxxxx>]

Hi Dscho

On 18/11/2022 13:40, Johannes Schindelin wrote:
> Hi Phillip,
>
> On Thu, 10 Nov 2022, Phillip Wood via GitGitGadget wrote:
>
> > From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
> >
> > The arguments to the `reset` and `merge` commands may be a label created
> > with a `label` command or an arbitrary commit name. The `merge` command
> > uses the lookup_label() function to lookup its arguments but `reset` has
> > a slightly different version of that function in do_reset(). Reduce this
> > code duplication by calling lookup_label() from do_reset() as well.
> >
> > This change improves the behavior of `reset` when the argument is a
> > tree.  Previously `reset` would accept a tree only for the rebase to
> > fail with
> >
> >         update_ref failed for ref 'HEAD': cannot update ref 'HEAD': trying to write non-commit object da5497437fd67ca928333aab79c4b4b55036ea66 to branch 'HEAD'
> >
> > Using lookup_label() means do_reset() will now error out straight away
> > if its argument is not a commit.
> >
> > Signed-off-by: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
> > ---
>
> Very nice.
>
>  From reading the patch, I get the impression that this also addresses
> https://github.com/gitgitgadget/git/issues/199, i.e. allowing `reset
> <tag>`.
>
> Am I right?
> Dscho

I think so, the tag will be dereferenced by lookup_commit_reference()

Best Wishes

Phillip

> P.S.: FWIW here is my ACK for both patches.
>
> >   sequencer.c              | 49 ++++++++++++++++++++--------------------
> >   t/t3430-rebase-merges.sh |  8 +++++++
> >   2 files changed, 33 insertions(+), 24 deletions(-)
> >
> > diff --git a/sequencer.c b/sequencer.c
> > index e658df7e8ff..21f5032df0d 100644
> > --- a/sequencer.c
> > +++ b/sequencer.c
> > @@ -3696,6 +3696,26 @@ static const char *reflog_message(struct replay_opts *opts,
> >   	return buf.buf;
> >   }
> >
> > +static struct commit *lookup_label(const char *label, int len,
> > +				   struct strbuf *buf)
> > +{
> > +	struct commit *commit;
> > +
> > +	strbuf_reset(buf);
> > +	strbuf_addf(buf, "refs/rewritten/%.*s", len, label);
> > +	commit = lookup_commit_reference_by_name(buf->buf);
> > +	if (!commit) {
> > +		/* fall back to non-rewritten ref or commit */
> > +		strbuf_splice(buf, 0, strlen("refs/rewritten/"), "", 0);
> > +		commit = lookup_commit_reference_by_name(buf->buf);
> > +	}
> > +
> > +	if (!commit)
> > +		error(_("could not resolve '%s'"), buf->buf);
> > +
> > +	return commit;
> > +}
> > +
> >   static int do_reset(struct repository *r,
> >   		    const char *name, int len,
> >   		    struct replay_opts *opts)
> > @@ -3727,6 +3747,7 @@ static int do_reset(struct repository *r,
> >   		oidcpy(&oid, &opts->squash_onto);
> >   	} else {
> >   		int i;
> > +		struct commit *commit;
> >
> >   		/* Determine the length of the label */
> >   		for (i = 0; i < len; i++)
> > @@ -3734,12 +3755,12 @@ static int do_reset(struct repository *r,
> >   				break;
> >   		len = i;
> >
> > -		strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
> > -		if (get_oid(ref_name.buf, &oid) &&
> > -		    get_oid(ref_name.buf + strlen("refs/rewritten/"), &oid)) {
> > -			ret = error(_("could not read '%s'"), ref_name.buf);
> > +		commit = lookup_label(name, len, &ref_name);
> > +		if (!commit) {
> > +			ret = -1;
> >   			goto cleanup;
> >   		}
> > +		oid = commit->object.oid;
> >   	}
> >
> >   	setup_unpack_trees_porcelain(&unpack_tree_opts, "reset");
> > @@ -3786,26 +3807,6 @@ cleanup:
> >   	return ret;
> >   }
> >
> > -static struct commit *lookup_label(const char *label, int len,
> > -				   struct strbuf *buf)
> > -{
> > -	struct commit *commit;
> > -
> > -	strbuf_reset(buf);
> > -	strbuf_addf(buf, "refs/rewritten/%.*s", len, label);
> > -	commit = lookup_commit_reference_by_name(buf->buf);
> > -	if (!commit) {
> > -		/* fall back to non-rewritten ref or commit */
> > -		strbuf_splice(buf, 0, strlen("refs/rewritten/"), "", 0);
> > -		commit = lookup_commit_reference_by_name(buf->buf);
> > -	}
> > -
> > -	if (!commit)
> > -		error(_("could not resolve '%s'"), buf->buf);
> > -
> > -	return commit;
> > -}
> > -
> >   static int do_merge(struct repository *r,
> >   		    struct commit *commit,
> >   		    const char *arg, int arg_len,
> > diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
> > index f351701fec2..fbbc4439bfe 100755
> > --- a/t/t3430-rebase-merges.sh
> > +++ b/t/t3430-rebase-merges.sh
> > @@ -138,6 +138,14 @@ test_expect_success '`reset` refuses to overwrite untracked files' '
> >   	git rebase --abort
> >   '
> >
> > +test_expect_success '`reset` rejects trees' '
> > +	test_when_finished "test_might_fail git rebase --abort" &&
> > +	test_must_fail env GIT_SEQUENCE_EDITOR="echo reset A^{tree} >" \
> > +		git rebase -i B C >out 2>err &&
> > +	grep "object .* is a tree" err &&
> > +	test_must_be_empty out
> > +'
> > +
> >   test_expect_success 'failed `merge -C` writes patch (may be rescheduled, too)' '
> >   	test_when_finished "test_might_fail git rebase --abort" &&
> >   	git checkout -b conflicting-merge A &&
> > --
> > gitgitgadget