Subject: Re: [PATCH] fetch: Fix segfault on pull --set-upstream outside a branch.

From: Junio C Hamano <[email-masked]>
Date: Tue, 06 Jul 2021 12:48:16 -0700

Junio C Hamano <[email-masked]> writes:

> Nit.  What do you mean by "outside a branch"?  If you mean "when the
> HEAD is detached", please say so, and use the same terminology in
> your warning message.

Here is what I queued for today's integration run.  Eric's
suggestion to add a simple test is a good idea, too.

Thanks.

-- >8 --
From: Clemens Fruhwirth <[email-masked]>
Date: Tue, 6 Jul 2021 18:22:38 +0200
Subject: [PATCH] fetch: fix segfault on pull --set-upstream while on a detached HEAD

branch_get("HEAD") can return NULL, when HEAD is detached, and cause
the code to segfault when the user calls "pull --set-upstream".

Catch this case and warn the user to avoid a segfault.

Signed-off-by: Clemens Fruhwirth <[email-masked]>
Signed-off-by: Junio C Hamano <[email-masked]>
---
 builtin/fetch.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/builtin/fetch.c b/builtin/fetch.c
index dfde96a435..0a11430df4 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -1602,6 +1602,10 @@ static int do_fetch(struct transport *transport,
 		struct ref *rm;
 		struct ref *source_ref = NULL;
 
+		if (!branch) {
+			warning(_("no branch detected to use --set-upstream with."));
+			goto skip;
+		}
 		/*
 		 * We're setting the upstream configuration for the
 		 * current branch. The relevant upstream is the
-- 
2.32.0-288-g654beb0eda