[PATCH v2 1/6] test-lib: introduce test_commit_bulk

[Jeff King <peff@peff.net>]

Here's a re-roll of just the first patch of this series, since that was
the one that got all the comments (and the others are textually
independent).

The changes are:

  - drop the leftover in_dir assignment

  - replace ${indir:+} magic with defaulting indir=. (so we always pass
    it to "-C"

  - replace eval formatting magic with "%s" printf formatters (safer and
    gets rid of quoting issues in the callers).

  - use a tempfile to avoid significant logic on the left-hand subshell
    of a pipe. This actually  _doesn't_ save a process because we end up
    having to call "rm" to get rid of the tempfile. But I think it makes
    the logic easier to follow (we can get just call test_tick as normal
    in our loop), and as a bonus it leaves something you can inspect if
    the fast-import fails.

  - I dropped the comparison to test_commit in the documentation, since
    it isn't a direct replacement due to the lack of tag creation. I
    think that makes it clear enough.

    I _didn't_ move the documentation out to t/README. IMHO we should be
    moving in the opposite direction. But either way, I think it's
    something we should handle separately (either consistently moving it
    all into t/README, or moving it closer to the definitions).

I didn't re-run all of the timings, but I spot-checked a few and got
similar improvements (weirdly all of my timings, both before and after,
seem slightly faster today; apparently gremlins were slowing my machine
down yesterday?).

-- >8 --
Subject: 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

So we're over 20% faster, while making the callers slightly shorter. We
added a lot more lines in test-lib-function.sh, of course, and the
helper is way more featureful than we need here. But my hope is that it
will be flexible enough to use in more places.

Signed-off-by: Jeff King <peff@peff.net>
---
 t/t5310-pack-bitmaps.sh |  15 +----
 t/test-lib-functions.sh | 123 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 126 insertions(+), 12 deletions(-)

diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index a26c8ba9a2..3aab7024ca 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -21,15 +21,9 @@ has_any () {
 }
 
 test_expect_success 'setup repo with moderate-sized history' '
-	for i in $(test_seq 1 10)
-	do
-		test_commit $i
-	done &&
+	test_commit_bulk --id=file 10 &&
 	git checkout -b other HEAD~5 &&
-	for i in $(test_seq 1 10)
-	do
-		test_commit side-$i
-	done &&
+	test_commit_bulk --id=side 10 &&
 	git checkout master &&
 	bitmaptip=$(git rev-parse master) &&
 	blob=$(echo tagged-blob | git hash-object -w --stdin) &&
@@ -106,10 +100,7 @@ test_expect_success 'clone from bitmapped repository' '
 '
 
 test_expect_success 'setup further non-bitmapped commits' '
-	for i in $(test_seq 1 10)
-	do
-		test_commit further-$i
-	done
+	test_commit_bulk --id=further 10
 '
 
 rev_list_tests 'partial bitmap'
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 0367cec5fd..9fd0fa2a89 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -233,6 +233,129 @@ test_merge () {
 	git tag "$1"
 }
 
+# Efficiently create <nr> commits, each with a unique number (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 %s")
+#   --filename=<fn>:
+#	modify <fn> in each commit (default: %s.t)
+#   --contents=<string>:
+#	place <string> in each file (default: "content %s")
+#   --id=<string>:
+#	shorthand to use <string> and %s in message, filename, and contents
+#
+# The message, filename, and contents strings are evaluated by printf, with the
+# first "%s" replaced by the current commit number. So you can do:
+#
+#   test_commit_bulk --filename=file --contents="modification %s"
+#
+# to have every commit touch the same file, but with unique content.
+#
+test_commit_bulk () {
+	tmpfile=.bulk-commit.input
+	indir=.
+	ref=HEAD
+	n=1
+	message='commit %s'
+	filename='%s.t'
+	contents='content %s'
+	while test $# -gt 0
+	do
+		case "$1" in
+		-C)
+			indir=$2
+			shift
+			;;
+		--ref=*)
+			ref=${1#--*=}
+			;;
+		--start=*)
+			n=${1#--*=}
+			;;
+		--message=*)
+			message=${1#--*=}
+			;;
+		--filename=*)
+			filename=${1#--*=}
+			;;
+		--contents=*)
+			contents=${1#--*=}
+			;;
+		--id=*)
+			message="${1#--*=} %s"
+			filename="${1#--*=}-%s.t"
+			contents="${1#--*=} %s"
+			;;
+		-*)
+			BUG "invalid test_commit_bulk option: $1"
+			;;
+		*)
+			break
+			;;
+		esac
+		shift
+	done
+	total=$1
+
+	{
+		# A "reset ... from" instructs fastimport to build on an
+		# existing branch tip rather than trying to overwrite.
+		if tip=$(git -C "$indir" rev-parse --verify "$ref" 2>/dev/null)
+		then
+			echo "reset $ref"
+			echo "from $tip"
+		fi
+
+		while test "$total" -gt 0
+		do
+			test_tick &&
+			echo "commit $ref"
+			printf 'author %s <%s> %s\n' \
+				"$GIT_AUTHOR_NAME" \
+				"$GIT_AUTHOR_EMAIL" \
+				"$GIT_AUTHOR_DATE"
+			printf 'committer %s <%s> %s\n' \
+				"$GIT_COMMITTER_NAME" \
+				"$GIT_COMMITTER_EMAIL" \
+				"$GIT_COMMITTER_DATE"
+			echo "data <<EOF"
+			printf "$message\n" $n
+			echo "EOF"
+			printf "M 644 inline $filename\n" $n
+			echo "data <<EOF"
+			printf "$contents\n" $n
+			echo "EOF"
+			echo
+			n=$((n + 1))
+			total=$((total - 1))
+		done
+
+	} >"$tmpfile"
+
+	git -C "$indir" \
+	    -c fastimport.unpacklimit=0 \
+	    fast-import <"$tmpfile" || return 1
+
+	# This will be left in place on failure, which may aid debugging.
+	rm -f "$tmpfile"
+
+	# If we updated HEAD, then be nice and update the index and working
+	# tree, too.
+	if test "$ref" = "HEAD"
+	then
+		git -C "$indir" checkout -f HEAD || return 1
+	fi
+
+}
+
 # This function helps systems where core.filemode=false is set.
 # Use it instead of plain 'chmod +x' to set or unset the executable bit
 # of a file in the working directory and add it to the index.
-- 
2.22.0.775.g4ba9815492