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

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Phillip,

On Thu, 10 Nov 2022, Phillip Wood via GitGitGadget wrote:

> From: Phillip Wood <phillip.wood@dunelm.org.uk>
>
> 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@dunelm.org.uk>
> ---

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

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
>
>