fsck --name-objects: be more careful parsing generation numbers

dscho · gitster · commit e89f89361cd7 · 2021-02-10T12:38:05.000-08:00
In 7b35efd (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>
diff --git 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
@@ -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
 	)
 '
 

Original file line number	Diff line number	Diff line change
`@@ -461,6 +461,11 @@ static int fsck_walk_commit(struct commit commit, void data, struct fsck_optio`
`461`	`461`	`generation += power * (name[--len] - '0');`
`462`	`462`	`if (power > 1 && len && name[len - 1] == '~')`
`463`	`463`	`name_prefix_len = len - 1;`
	`464`	`+ else {`
	`465`	`+ /* Maybe a non-first parent, e.g. HEAD^2 */`
	`466`	`+ generation = 0;`
	`467`	`+ name_prefix_len = len;`
	`468`	`+ }`
`464`	`469`	`}`
`465`	`470`	`}`
`466`	`471`
Original file line number	Diff line number	Diff line change
`@@ -658,13 +658,15 @@ test_expect_success 'fsck --name-objects' '`
`658`	`658`	`git init name-objects &&`
`659`	`659`	`(`
`660`	`660`	`cd name-objects &&`
	`661`	`+ git config core.logAllRefUpdates false &&`
`661`	`662`	`test_commit julius caesar.t &&`
`662`		`- test_commit augustus &&`
`663`		`- test_commit caesar &&`
	`663`	`+ test_commit augustus44 &&`
	`664`	`+ test_commit caesar &&`
`664`	`665`	`remove_object $(git rev-parse julius:caesar.t) &&`
`665`		`- test_must_fail git fsck --name-objects >out &&`
`666`	`666`	`tree=$(git rev-parse --verify julius:) &&`
`667`		`- test_i18ngrep "$tree (refs/tags/julius:" out`
	`667`	`+ git tag -d julius &&`
	`668`	`+ test_must_fail git fsck --name-objects >out &&`
	`669`	`+ test_i18ngrep "$tree (refs/tags/augustus44\\^:" out`
`668`	`670`	`)`
`669`	`671`	`'`
`670`	`672`