Merge branch 'ds/name-hash-tweaks'

"git pack-objects" and its wrapper "git repack" learned an option
to use an alternative path-hash function to improve delta-base
selection to produce a packfile with deeper history than window
size.

* ds/name-hash-tweaks:
  pack-objects: prevent name hash version change
  test-tool: add helper for name-hash values
  p5313: add size comparison test
  pack-objects: add GIT_TEST_NAME_HASH_VERSION
  repack: add --name-hash-version option
  pack-objects: add --name-hash-version option
  pack-objects: create new name-hash function version

1 files changed, 34 insertions, 1 deletions

diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index eabfcd7ff6..621bbbdd26 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -26,6 +26,36 @@ has_any () {
 	grep -Ff "$1" "$2"
 }
 
+# Since name-hash values are stored in the .bitmap files, add a test
+# that checks that the name-hash calculations are stable across versions.
+# Not exhaustive, but these hashing algorithms would be hard to change
+# without causing deviations here.
+test_expect_success 'name-hash value stability' '
+	cat >names <<-\EOF &&
+	first
+	second
+	third
+	a/one-long-enough-for-collisions
+	b/two-long-enough-for-collisions
+	many/parts/to/this/path/enough/to/collide/in/v2
+	enough/parts/to/this/path/enough/to/collide/in/v2
+	EOF
+
+	test-tool name-hash <names >out &&
+
+	cat >expect <<-\EOF &&
+	2582249472 1763573760 first
+	2289942528 1188134912 second
+	2300837888 1130758144 third
+	2544516325 3963087891 a/one-long-enough-for-collisions
+	2544516325 4013419539 b/two-long-enough-for-collisions
+	1420111091 1709547268 many/parts/to/this/path/enough/to/collide/in/v2
+	1420111091 1709547268 enough/parts/to/this/path/enough/to/collide/in/v2
+	EOF
+
+	test_cmp expect out
+'
+
 test_bitmap_cases () {
 	writeLookupTable=false
 	for i in "$@"
@@ -419,7 +449,10 @@ test_bitmap_cases () {
 			cat >expect <<-\EOF &&
 			error: missing value for '\''pack.preferbitmaptips'\''
 			EOF
-			git repack -adb 2>actual &&
+
+			# Disable name hash version adjustment due to stderr comparison.
+			GIT_TEST_NAME_HASH_VERSION=1 \
+				git repack -adb 2>actual &&
 			test_cmp expect actual
 		)
 	'