gpg-interface: handle bool user.signingkey

The config handler for user.signingkey does not check for a
boolean value, and thus:

  git -c user.signingkey tag

will segfault. We could fix this and even shorten the code
by using git_config_string(). But our set_signing_key()
helper is used by other code outside of gpg-interface.c, so
we must keep it (and we may as well use it, because unlike
git_config_string() it does not leak when we overwrite an
old value).

Ironically, the handler for gpg.program just below _could_
use git_config_string() but doesn't. But since we're going
to touch that in a future patch, we'll leave it alone for
now. We will add some whitespace and returns in preparation
for adding more config keys, though.

Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Ben Toews <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

gpg-interface.c

@@ -128,13 +128,19 @@ void set_signing_key(const char *key)
 int git_gpg_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "user.signingkey")) {
+		if (!value)
+			return config_error_nonbool(var);
 		set_signing_key(value);
+		return 0;
 	}
+
 	if (!strcmp(var, "gpg.program")) {
 		if (!value)
 			return config_error_nonbool(var);
 		gpg_program = xstrdup(value);
+		return 0;
 	}
+
 	return 0;
 }