[PATCH 09/11] merge: use git_config_string_dup() for pull strategies

[Jeff King <peff@peff.net>]

Converting pull.twohead and pull.octopus to use git_config_string_dup()
fixes possible leaks if we see those config variables defined multiple
times. Doing so is mostly an "easy" case, except that we later may
assign a string literal to pull_twohead (which is now a non-const
pointer).

That's actually not _too_ bad in practice, as it happens after we've
done all of our config parsing (so nobody would try to free it). And the
compiler won't complain unless -Wwrite-strings is used (and turning that
on creates a host of other warnings, some useful and some not). But
while we're here let's future proof it as best we can.

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/merge.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/builtin/merge.c b/builtin/merge.c
index c2be29ed2f..a9e5100e70 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -101,7 +101,7 @@ static struct strategy all_strategy[] = {
 	{ "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
 };
 
-static const char *pull_twohead, *pull_octopus;
+static char *pull_twohead, *pull_octopus;
 
 enum ff_type {
 	FF_NO,
@@ -615,9 +615,9 @@ static int git_merge_config(const char *k, const char *v,
 	else if (!strcmp(k, "merge.verifysignatures"))
 		verify_signatures = git_config_bool(k, v);
 	else if (!strcmp(k, "pull.twohead"))
-		return git_config_string(&pull_twohead, k, v);
+		return git_config_string_dup(&pull_twohead, k, v);
 	else if (!strcmp(k, "pull.octopus"))
-		return git_config_string(&pull_octopus, k, v);
+		return git_config_string_dup(&pull_octopus, k, v);
 	else if (!strcmp(k, "commit.cleanup"))
 		return git_config_string_dup(&cleanup_arg, k, v);
 	else if (!strcmp(k, "merge.ff")) {
@@ -1291,7 +1291,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	if (!pull_twohead) {
 		char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
 		if (default_strategy && !strcmp(default_strategy, "ort"))
-			pull_twohead = "ort";
+			pull_twohead = xstrdup("ort");
 	}
 
 	init_diff_ui_defaults();
-- 
2.44.0.872.g288abe5b5b