From 8c891eed3a89ff945b7957cdf62037b2e2b6eca7 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Wed, 10 Feb 2021 18:01:29 +0000
Subject: [PATCH 1/2] t1450: robustify `remove_object()`

This function can be simplified by using the `test_oid_to_path()`
helper, which incidentally also makes it more robust by not relying on
the exact file system layout of the loose object files.

While at it, do not define those functions in a test case, it buys us
nothing.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 t/t1450-fsck.sh | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index b17f5c21fb..0c58cb349b 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -40,17 +40,13 @@ test_expect_success 'HEAD is part of refs, valid objects appear valid' '
 # specific corruption you test afterwards, lest a later test trip over
 # it.
 
-test_expect_success 'setup: helpers for corruption tests' '
-	sha1_file() {
-		remainder=${1#??} &&
-		firsttwo=${1%$remainder} &&
-		echo ".git/objects/$firsttwo/$remainder"
-	} &&
+sha1_file () {
+	git rev-parse --git-path objects/$(test_oid_to_path "$1")
+}
 
-	remove_object() {
-		rm "$(sha1_file "$1")"
-	}
-'
+remove_object () {
+	rm "$(sha1_file "$1")"
+}
 
 test_expect_success 'object with bad sha1' '
 	sha=$(echo blob | git hash-object -w --stdin) &&

From e89f89361cd7b706858eb22a6cf3d59d31a00acf Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Wed, 10 Feb 2021 18:01:30 +0000
Subject: [PATCH 2/2] fsck --name-objects: be more careful parsing generation
 numbers

In 7b35efd734e (fsck_walk(): optionally name objects on the go,
2016-07-17), the `fsck` machinery learned to optionally name the
objects, so that it is easier to see what part of the repository is in a
bad shape, say, when objects are missing.

To save on complexity, this machinery uses a parser to determine the
name of a parent given a commit's name: any `~<n>` suffix is parsed and
the parent's name is formed from the prefix together with `~<n+1>`.

However, this parser has a bug: if it finds a suffix `<n>` that is _not_
`~<n>`, it will mistake the empty string for the prefix and `<n>` for
the generation number. In other words, it will generate a name of the
form `~<bogus-number>`.

Let's fix this.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 fsck.c          |  5 +++++
 t/t1450-fsck.sh | 10 ++++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fsck.c b/fsck.c
index 5e282b3b6b..293c1a2ef5 100644
--- a/fsck.c
+++ b/fsck.c
@@ -461,6 +461,11 @@ static int fsck_walk_commit(struct commit *commit, void *data, struct fsck_optio
 				generation += power * (name[--len] - '0');
 			if (power > 1 && len && name[len - 1] == '~')
 				name_prefix_len = len - 1;
+			else {
+				/* Maybe a non-first parent, e.g. HEAD^2 */
+				generation = 0;
+				name_prefix_len = len;
+			}
 		}
 	}
 
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 0c58cb349b..d3a3d2722b 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -658,13 +658,15 @@ test_expect_success 'fsck --name-objects' '
 	git init name-objects &&
 	(
 		cd name-objects &&
+		git config core.logAllRefUpdates false &&
 		test_commit julius caesar.t &&
-		test_commit augustus &&
-		test_commit caesar &&
+		test_commit augustus44 &&
+		test_commit caesar  &&
 		remove_object $(git rev-parse julius:caesar.t) &&
-		test_must_fail git fsck --name-objects >out &&
 		tree=$(git rev-parse --verify julius:) &&
-		test_i18ngrep "$tree (refs/tags/julius:" out
+		git tag -d julius &&
+		test_must_fail git fsck --name-objects >out &&
+		test_i18ngrep "$tree (refs/tags/augustus44\\^:" out
 	)
 '