Re: [PATCH v1 1/1] rev-list: add --missing=print-only mode

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

On 20/04/2026 08:43, Patrick Steinhardt wrote:
> On Sun, Apr 19, 2026 at 02:18:40PM +0530, Siddharth Asthana wrote:
> 
>>   static struct oidmap missing_objects;
>>   enum missing_action {
>> -	MA_ERROR = 0,    /* fail if any missing objects are encountered */
>> -	MA_ALLOW_ANY,    /* silently allow ALL missing objects */
>> -	MA_PRINT,        /* print ALL missing objects in special section */
>> -	MA_PRINT_INFO,   /* same as MA_PRINT but also prints missing object info */
>> +	MA_ERROR = 0, /* fail if any missing objects are encountered */
>> +	MA_ALLOW_ANY, /* silently allow ALL missing objects */
>> +	MA_PRINT, /* print ALL missing objects in special section */
>> +	MA_PRINT_INFO, /* same as MA_PRINT but also prints missing object info */
>> +	MA_PRINT_ONLY, /* print ONLY missing objects, without the "?" prefix */
> 
> Makes me wonder whether we'll eventually also want to have
> `MA_PRINT_INFO_ONLY`.

Perhaps we'd be better to add a "--missing-only" option that limits the 
output to missing objects? That would avoid the problem of 
"--missing=print-only" not really explaining what it does as well.

>> +for obj in "HEAD~1" "HEAD~1^{tree}" "HEAD:1.t"
>> +do
>> +	test_expect_success "rev-list --missing=print-only with missing $obj" '
>> +		oid="$(git rev-parse $obj)" &&
>> +		path=".git/objects/$(test_oid_to_path $oid)" &&
>> +
>> +		# Capture present OIDs before hiding anything.
>> +		git rev-list --objects --no-object-names HEAD ^$obj >present.raw &&
>> +
>> +		mv "$path" "$path.hidden" &&
>> +		test_when_finished "mv $path.hidden $path" &&
>> +
>> +		git rev-list --missing=print-only --objects --no-object-names \
>> +			HEAD >actual &&
>> +
>> +		# Only the missing OID should appear, without the "?" prefix.
>> +		grep "^$oid$" actual &&
>> +
>> +		# Present objects must NOT appear in the output.
>> +		while read present_oid
>> +		do
>> +			! grep "^$present_oid$" actual || return 1
>> +		done <present.raw
> 
> How many present object IDs do we have? I'm a bit worried that we now
> execute grep(1) hundreds of times. Can we maybe do some tricks with
> comm(1) instead?

If we want to verify that it only prints a single oid then

	echo $oid >expect &&
	test_cmp expect actual

would be much simpler more helpful if the test fails

Thanks

Phil