Re: [PATCH v3 07/20] commit-graph: verify catches corrupt signature

> Derrick Stolee <dstolee@microsoft.com> writes:
>
>> This is the first of several commits that add a test to check that
>> 'git commit-graph verify' catches corruption in the commit-graph
>> file. The first test checks that the command catches an error in
>> the file signature. This is a check that exists in the existing
>> commit-graph reading code.
> Good start.
>
> This handles 3 out of 5 checks in load_commit_graph_one().  The
> remaining are:
> * too short file (length smaller than minimal commit-graph size)
> * more than one chunk of one of 4 defined types
>
>> Add a helper method 'corrupt_graph_and_verify' to the test script
>> t5318-commit-graph.sh. This helper corrupts the commit-graph file
>> at a certain location, runs 'git commit-graph verify', and reports
>> the output to the 'err' file. This data is filtered to remove the
>> lines added by 'test_must_fail' when the test is run verbosely.
>> Then, the output is checked to contain a specific error message.
> Thanks for an explanation.
>
>> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
>> ---
>>   t/t5318-commit-graph.sh | 43 +++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 43 insertions(+)
>>
>> diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
>> index 6ca451dfd2..bd64481c7a 100755
>> --- a/t/t5318-commit-graph.sh
>> +++ b/t/t5318-commit-graph.sh
>> @@ -235,9 +235,52 @@ test_expect_success 'perform fast-forward merge in full repo' '
>>   	test_cmp expect output
>>   '
>>   
>> +# the verify tests below expect the commit-graph to contain
>> +# exactly the commits reachable from the commits/8 branch.
>> +# If the file changes the set of commits in the list, then the
>> +# offsets into the binary file will result in different edits
>> +# and the tests will likely break.
>> +
>>   test_expect_success 'git commit-graph verify' '
>>   	cd "$TRASH_DIRECTORY/full" &&
>> +	git rev-parse commits/8 | git commit-graph write --stdin-commits &&
>>   	git commit-graph verify >output
>>   '
> I don't quite understand what the change is meant to do.

> Also, as I said earlier, I'd prefer if tests were as indpendent of each
> other as possible, to make running individual tests (e.g. only
> previously falling tests) easier.
>
> I especially do not like mixing running actual test with setting up the
> repository for future tests, as here.
>
>>   
>> +GRAPH_BYTE_VERSION=4
>> +GRAPH_BYTE_HASH=5
>> +
>> +# usage: corrupt_graph_and_verify <position> <data> <string>
>> +# Manipulates the commit-graph file at the position
>> +# by inserting the data, then runs 'git commit-graph verify'
>> +# and places the output in the file 'err'. Test 'err' for
>> +# the given string.
> Very nice to have this description.
>
>> +corrupt_graph_and_verify() {
>> +	pos=$1
>> +	data="${2:-\0}"
>> +	grepstr=$3
>> +	cd "$TRASH_DIRECTORY/full" &&
>> +	test_when_finished mv commit-graph-backup $objdir/info/commit-graph &&
>> +	cp $objdir/info/commit-graph commit-graph-backup &&
>> +	printf "$data" | dd of="$objdir/info/commit-graph" bs=1 seek="$pos" conv=notrunc &&
> Using 'printf' with octal is much more portable than relying on 'echo'
> supporting octal escape sequences (or supporting escape sequences at
> all).
>
>> +	test_must_fail git commit-graph verify 2>test_err &&
>> +	grep -v "^+" test_err >err
>> +	grep "$grepstr" err
> Shouldn't this last 'grep' be 'test_i18ngrep' instead, to allow for
> translated messages from 'git commit-graph verify' / 'git fsck'?
>
>> +}
> This function makes actual tests short and simple, without duplicated
> code.  Very good.
>
>> +
>> +test_expect_success 'detect bad signature' '
>> +	corrupt_graph_and_verify 0 "\0" \
>> +		"graph signature"
>> +'
>> +
>> +test_expect_success 'detect bad version' '
>> +	corrupt_graph_and_verify $GRAPH_BYTE_VERSION "\02" \
>> +		"graph version"
>> +'
>> +
>> +test_expect_success 'detect bad hash version' '
>> +	corrupt_graph_and_verify $GRAPH_BYTE_HASH "\02" \
> When we move from SHA-1 (hash version 1) to NewHash (hash version 2),
> this test would start failing... which is actually not a bad idea.
>
>> +		"hash version"
>> +'
>> +
>>   test_done