Re: [PATCH 1/6] test-lib: introduce test_commit_bulk

> Some tests need to create a string of commits. Doing this with
> test_commit is very heavy-weight, as it needs at least one process per
> commit (and in fact, uses several).
> 
> For bulk creation, we can do much better by using fast-import, but it's
> often a pain to generate the input. Let's provide a helper to do so.

> We'll use t5310 as a guinea pig, as it has three 10-commit loops. Here
> are hyperfine results before and after:
> 
>   [before]
>   Benchmark #1: ./t5310-pack-bitmaps.sh --root=/var/ram/git-tests
>     Time (mean ± σ):      2.846 s ±  0.305 s    [User: 3.042 s, System: 0.919 s]
>     Range (min … max):    2.250 s …  3.210 s    10 runs
> 
>   [after]
>   Benchmark #1: ./t5310-pack-bitmaps.sh --root=/var/ram/git-tests
>     Time (mean ± σ):      2.210 s ±  0.174 s    [User: 2.570 s, System: 0.604 s]
>     Range (min … max):    1.999 s …  2.590 s    10 runs

> +# Similar to test_commit, but efficiently create <nr> commits, each with a
> +# unique number $n (from 1 to <nr> by default) in the commit message.
> +#
> +# Usage: test_commit_bulk [options] <nr>
> +#   -C <dir>:
> +#	Run all git commands in directory <dir>
> +#   --ref=<n>:
> +#	ref on which to create commits (default: HEAD)
> +#   --start=<n>:
> +#	number commit messages from <n> (default: 1)
> +#   --message=<msg>:
> +#	use <msg> as the commit mesasge (default: "commit $n")
> +#   --filename=<fn>:
> +#	modify <fn> in each commit (default: $n.t)
> +#   --contents=<string>:
> +#	place <string> in each file (default: "content $n")
> +#   --id=<string>:
> +#	shorthand to use <string> and $n in message, filename, and contents
> +#
> +# The message, filename, and contents strings are evaluated by the shell inside
> +# double-quotes, with $n set to the current commit number. So you can do:
> +#
> +#   test_commit_bulk --filename=file --contents='modification $n'
> +#
> +# to have every commit touch the same file, but with unique content. Spaces are
> +# OK, but you must escape any metacharacters (like backslashes or
> +# double-quotes) you do not want expanded.
> +#

> +		while test "$total" -gt 0
> +		do
> +			echo "commit $ref" &&
> +			printf 'author %s <%s> %s\n' \
> +				"$GIT_AUTHOR_NAME" \
> +				"$GIT_AUTHOR_EMAIL" \
> +				"$cur_time -0700" &&
> +			printf 'committer %s <%s> %s\n' \
> +				"$GIT_COMMITTER_NAME" \
> +				"$GIT_COMMITTER_EMAIL" \
> +				"$cur_time -0700" &&
> +			echo "data <<EOF" &&
> +			eval "echo \"$message\"" &&
> +			echo "EOF" &&
> +			eval "echo \"M 644 inline $filename\"" &&
> +			echo "data <<EOF" &&
> +			eval "echo \"$contents\"" &&
> +			echo "EOF" &&
> +			echo &&
> +			n=$((n + 1)) &&
> +			cur_time=$((cur_time + 1)) &&
> +			total=$((total - 1)) ||
> +			echo "poison fast-import stream"
> +		done