[PATCH v3 3/3] Add a perf test for rebase -i

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: May 13, 2016, 13:26 UTC
Message-ID: <d5d1a6251a2e80700bd295bcdb48a99ab976493f.1463145936.git.johannes.schindelin@gmx.de>
In-Reply-To: <cover.1463145936.git.johannes.schindelin@gmx.de>

This developer spent a lot of time trying to speed up the interactive rebase, in particular on Windows. And will continue to do so.

To make it easier to demonstrate the performance improvement, let's have a reproducible performance test.

The topic branch we use to test performance was found using these shell commands (essentially searching for a long-enough topic branch in Git's own history that touched the same file multiple times):

	git rev-list --parents origin/master |
	grep ' .* ' |
	while read commit rest
	do
		patch_count=$(git rev-list --count $commit^..$commit^2)
		test $patch_count -gt 20 || continue

		merges="$(git rev-list --parents $commit^..$commit^2 |
			grep ' .* ')"
		test -z "$merges" || continue

		patches_per_file="$(git log --pretty=%H --name-only \
				$commit^..$commit^2 |
			grep -v '^$' |
			sort |
			uniq -c -d |
			sort -n -r)"
		test -n "$patches_per_file" &&
		test 20 -lt $(echo "$patches_per_file" |
			sed -n '1s/^ *\([0-9]*\).*/\1/p') || continue

		printf 'commit %s\n%s\n' "$commit" "$patches_per_file"
	done

Note that we can get away with *not* having to reset to the original branch tip before rebasing: we switch the first two "pick" lines every time, so we end up with the same patch order after two rebases, and the complexity of both rebases is equivalent.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 t/perf/p3404-rebase-interactive.sh | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100755 t/perf/p3404-rebase-interactive.sh

diff --git a/t/perf/p3404-rebase-interactive.sh b/t/perf/p3404-rebase-interactive.sh
new file mode 100755
index 0000000..88f47de
--- /dev/null
+++ b/t/perf/p3404-rebase-interactive.sh
@@ -0,0 +1,36 @@
+#!/bin/sh
+
+test_description='Tests rebase -i performance'
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+# This commit merges a sufficiently long topic branch for reasonable
+# performance testing
+branch_merge=ba5312da19c6fdb6c6747d479f58932aae6e900c^{commit}
+export branch_merge
+
+git rev-parse --verify $branch_merge >/dev/null 2>&1 || {
+	skip_all='skipping because $branch_merge was not found'
+	test_done
+}
+
+write_script swap-first-two.sh <<\EOF
+case "$1" in
+*/COMMIT_EDITMSG)
+	mv "$1" "$1".bak &&
+	sed -e '1{h;d}' -e 2G <"$1".bak >"$1"
+	;;
+esac
+EOF
+
+test_expect_success 'setup' '
+	git config core.editor "\"$PWD"/swap-first-two.sh\" &&
+	git checkout -f $branch_merge^2
+'
+
+test_perf 'rebase -i' '
+	git rebase -i $branch_merge^
+'
+
+test_done

-- 
2.8.2.465.gb077790