[PATCH/RFC] config: Give error message when not changing a multivar

When trying to set a multivar with "git config var value", "git config"
issues

warning: remote.repoor.push has multiple values

leaving the user under the impression that the operation succeeded,
unless one checks the return value.

Instead, make it

warning: remote.repoor.push has multiple values
error: Use a regexp, --add or --set-all to change remote.repoor.push.

to be clear and helpful.

Note: The "warning" is raised through other code paths also so that it
needs to remain a warning for these (which do not raise the error). Only
the caller can determine how to go on from that.

Signed-off-by: Michael J Gruber <redacted>
---
 builtin/config.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/builtin/config.c b/builtin/config.c
index 3e3c528..c438ef4 100644
--- a/builtin/config.c
+++ b/builtin/config.c

@@ -436,9 +436,13 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 			      NULL, NULL);
 	}
 	else if (actions == ACTION_SET) {
+		int ret;
 		check_argc(argc, 2, 2);
 		value = normalize_value(argv[0], argv[1]);
-		return git_config_set(argv[0], value);
+		ret = git_config_set(argv[0], value);
+		if (ret == 5)
+			error("Use a regexp, --add or --set-all to change %s.", argv[0]);
+		return ret;
 	}
 	else if (actions == ACTION_SET_ALL) {
 		check_argc(argc, 2, 3);

-- 
1.7.5.1.514.gd181fb