patcht3306,t5304: avoid clock skew issues

> On systems where the local time and file modification time may be out of
> sync (e.g. test directory on NFS) t3306 and t5305 can fail because prune
> compares times such as "now" (client time) with file modification times
> (server times for remote file systems). I.e., these are spurious test
> failures.
>
> Avoid this by setting the relevant modification times to the local time.
>
> Noticed on a system with as little as 2s time skew.
>
> Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
> ---
> I don't think we can safeguard prune itself properly. A filesystem may be out
> of time sync sporadically (and produce incorrect time stamps) but then be in
> sync when "git prune" is run so that we can't detect it.
>
>  t/t3306-notes-prune.sh |    4 ++++
>  t/t5304-prune.sh       |    3 ++-
>  2 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/t/t3306-notes-prune.sh b/t/t3306-notes-prune.sh
> index c428217..3114972 100755
> --- a/t/t3306-notes-prune.sh
> +++ b/t/t3306-notes-prune.sh
> @@ -20,6 +20,10 @@ test_expect_success 'setup: create a few commits with notes' '
>  	git add file3 &&
>  	test_tick &&
>  	git commit -m 3rd &&
> +	COMMIT=$(git rev-parse HEAD) &&
> +	COMMIT_FILE=.git/objects/$(echo $COMMIT | sed "s/^../&\//") &&

> Michael J Gruber <git@drmicha.warpmail.net> writes:
> 
>> On systems where the local time and file modification time may be out of
>> sync (e.g. test directory on NFS) t3306 and t5305 can fail because prune
>> compares times such as "now" (client time) with file modification times
>> (server times for remote file systems). I.e., these are spurious test
>> failures.
>>
>> Avoid this by setting the relevant modification times to the local time.
>>
>> Noticed on a system with as little as 2s time skew.
>>
>> Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
>> ---
>> I don't think we can safeguard prune itself properly. A filesystem may be out
>> of time sync sporadically (and produce incorrect time stamps) but then be in
>> sync when "git prune" is run so that we can't detect it.
>>
>>  t/t3306-notes-prune.sh |    4 ++++
>>  t/t5304-prune.sh       |    3 ++-
>>  2 files changed, 6 insertions(+), 1 deletions(-)
>>
>> diff --git a/t/t3306-notes-prune.sh b/t/t3306-notes-prune.sh
>> index c428217..3114972 100755
>> --- a/t/t3306-notes-prune.sh
>> +++ b/t/t3306-notes-prune.sh
>> @@ -20,6 +20,10 @@ test_expect_success 'setup: create a few commits with notes' '
>>  	git add file3 &&
>>  	test_tick &&
>>  	git commit -m 3rd &&
>> +	COMMIT=$(git rev-parse HEAD) &&
>> +	COMMIT_FILE=.git/objects/$(echo $COMMIT | sed "s/^../&\//") &&
> 
> Hmm, the remainder of the test script seems to know this commit is 5ee1c35
> all over the place.  Do the above two lines worth it?