builtin/blame: fix leaking prefixed paths

In `cmd_blame()` we compute prefixed paths by calling `add_prefix()`,
which itself calls `prefix_path()`. While `prefix_path()` returns an
allocated string, `add_prefix()` pretends to return a constant string.
Consequently, this path never gets freed.

Fix the return type to be `char *` and free the path to plug the memory
leak.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/blame.c

@@ -687,7 +687,7 @@ static unsigned parse_score(const char *arg)
 	return score;
 }
 
-static const char *add_prefix(const char *prefix, const char *path)
+static char *add_prefix(const char *prefix, const char *path)
 {
 	return prefix_path(prefix, prefix ? strlen(prefix) : 0, path);
 }
@@ -865,7 +865,7 @@ static void build_ignorelist(struct blame_scoreboard *sb,
 int cmd_blame(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info revs;
-	const char *path;
+	char *path = NULL;
 	struct blame_scoreboard sb;
 	struct blame_origin *o;
 	struct blame_entry *ent = NULL;
@@ -1226,6 +1226,7 @@ parse_done:
 	}
 
 cleanup:
+	free(path);
 	cleanup_scoreboard(&sb);
 	release_revisions(&revs);
 	return 0;

t/t6130-pathspec-noglob.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='test globbing (and noglob) of pathspec limiting'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'create commits with glob characters' '

t/t7010-setup.sh

@@ -2,6 +2,7 @@
 
 test_description='setup taking and sanitizing funny paths'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success setup '

t/t8003-blame-corner-cases.sh

@@ -4,6 +4,7 @@ test_description='git blame corner cases'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 pick_fc='s/^[0-9a-f^]* *\([^ ]*\) *(\([^ ]*\) .*/\1-\2/'

t/t8008-blame-formats.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 
 test_description='blame output in various formats on a simple case'
+
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 test_expect_success 'setup' '