gpg-interface: provide clear helper for struct signature_check

The struct has been growing members whose malloced memory needs to be
freed. Do this with one helper function so that no malloced memory shall
be left unfreed.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/merge.c

@@ -1282,10 +1282,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 				printf(_("Commit %s has a good GPG signature by %s\n"),
 				       hex, signature_check.signer);
 
-			free(signature_check.gpg_output);
-			free(signature_check.gpg_status);
-			free(signature_check.signer);
-			free(signature_check.key);
+			signature_check_clear(&signature_check);
 		}
 	}
 

gpg-interface.c

@@ -7,6 +7,18 @@
 static char *configured_signing_key;
 static const char *gpg_program = "gpg";
 
+void signature_check_clear(struct signature_check *sigc)
+{
+	free(sigc->gpg_output);
+	free(sigc->gpg_status);
+	free(sigc->signer);
+	free(sigc->key);
+	sigc->gpg_output = NULL;
+	sigc->gpg_status = NULL;
+	sigc->signer = NULL;
+	sigc->key = NULL;
+}
+
 void set_signing_key(const char *key)
 {
 	free(configured_signing_key);

gpg-interface.h

@@ -13,6 +13,7 @@ struct signature_check {
 	char *key;
 };
 
+extern void signature_check_clear(struct signature_check *sigc);
 extern int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key);
 extern int verify_signed_buffer(const char *payload, size_t payload_size, const char *signature, size_t signature_size, struct strbuf *gpg_output, struct strbuf *gpg_status);
 extern int git_gpg_config(const char *, const char *, void *);

pretty.c

@@ -1532,8 +1532,7 @@ void format_commit_message(const struct commit *commit,
 
 	free(context.commit_encoding);
 	logmsg_free(context.message, commit);
-	free(context.signature_check.gpg_output);
-	free(context.signature_check.signer);
+	signature_check_clear(&context.signature_check);
 }
 
 static void pp_header(struct pretty_print_context *pp,