Re: [PATCH v2 2/2] convert: Stream from fd to required clean filter instead of mmap

> The expectation on the process size is tested using /usr/bin/time.  An
> alternative would have been tcsh, which could be used to print memory
> information as follows:
> 
>     tcsh -c 'set time=(0 "%M"); <cmd>'
> 
> Although the logic could perhaps be simplified with tcsh, I chose to use
> 'time' to avoid a dependency on tcsh.

> @@ -190,6 +196,58 @@ test_expect_success 'required filter clean failure' '
>  	test_must_fail git add test.fc
>  '
>  
> +# Handle differences in /usr/bin/time.
> +#
> +#  - Linux: call with '-v'.
> +#    output: <spaces><description>:<space><value-in-KBytes>
> +#
> +#  - Mac: call with '-l'.
> +#    output: <spaces><value-in-Bytes><spaces><description>
> +#    Strip three digits to get to KB (base 10 is good enough).
> +#
> +case $(uname -s) in
> +Linux)
> +	test_set_prereq HAVE_MAX_MEM_USAGE
> +	max_mem_usage_KB () {
> +	    /usr/bin/time -v "$@" 2>&1 |
> +	    grep 'Maximum resident set size' |
> +	    cut -d ':' -f 2
> +	}
> +	;;
> +Darwin)
> +	test_set_prereq HAVE_MAX_MEM_USAGE
> +	max_mem_usage_KB () {
> +		/usr/bin/time -l "$@" 2>&1 |
> +		grep 'maximum resident set size' |
> +		sed -e 's/  */ /' |
> +		cut -d ' ' -f 2 |
> +		sed -e 's/...$//'
> +	}
> +	;;
> +esac
> +
> +max_mem_usage_is_lt_KB () {
> +	limit=$1
> +	shift
> +	mem_usage=$(max_mem_usage_KB "$@")
> +	if [ $mem_usage -lt $limit ]; then
> +		true
> +	else
> +		printf 'Command used too much memory (expected limit %dKB, actual usage %dKB).\n' \
> +			$limit $mem_usage
> +		false
> +	fi
> +}
> +
> +test_expect_success HAVE_MAX_MEM_USAGE \
> +'filtering large input to small output should use little memory' '
> +	git config filter.devnull.clean "cat >/dev/null" &&
> +	git config filter.devnull.required true &&
> +	for i in $(test_seq 1 30); do printf "%1048576d" 1; done >30MB &&
> +	echo "30MB filter=devnull" >.gitattributes &&
> +	max_mem_usage_is_lt_KB 15000 git add 30MB
> +'