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

[Phillip Wood <phillip.wood123@gmail.com>]

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@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

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
>>
>>