merge(3p/git): Merge git subtree at v2.29.2

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

third_party/git/t/t5411/test-0040-process-all-refs.sh

@@ -0,0 +1,113 @@
+test_expect_success "config receive.procReceiveRefs = refs ($PROTOCOL)" '
+	git -C "$upstream" config --unset-all receive.procReceiveRefs &&
+	git -C "$upstream" config --add receive.procReceiveRefs refs
+'
+
+# Refs of upstream : master(A)
+# Refs of workbench: master(A)  tags/v123
+test_expect_success "setup upstream branches ($PROTOCOL)" '
+	(
+		cd "$upstream" &&
+		git update-ref refs/heads/master $B &&
+		git update-ref refs/heads/foo $A &&
+		git update-ref refs/heads/bar $A &&
+		git update-ref refs/heads/baz $A
+	)
+
+'
+
+test_expect_success "setup proc-receive hook ($PROTOCOL)" '
+	write_script "$upstream/hooks/proc-receive" <<-EOF
+	printf >&2 "# proc-receive hook\n"
+	test-tool proc-receive -v \
+		-r "ok refs/heads/master" \
+		-r "option fall-through" \
+		-r "ok refs/heads/foo" \
+		-r "option fall-through" \
+		-r "ok refs/heads/bar" \
+		-r "option fall-through" \
+		-r "ok refs/for/master/topic" \
+		-r "option refname refs/pull/123/head" \
+		-r "option old-oid $A" \
+		-r "option new-oid $B" \
+		-r "ok refs/for/next/topic" \
+		-r "option refname refs/pull/124/head" \
+		-r "option old-oid $B" \
+		-r "option new-oid $A" \
+		-r "option forced-update"
+	EOF
+'
+
+# Refs of upstream : master(B)             foo(A)  bar(A))  baz(A)
+# Refs of workbench: master(A)  tags/v123
+# git push -f      : master(A)             (NULL)  (B)              refs/for/master/topic(A)  refs/for/next/topic(A)
+test_expect_success "proc-receive: process all refs ($PROTOCOL)" '
+	git -C workbench push -f origin \
+		HEAD:refs/heads/master \
+		:refs/heads/foo \
+		$B:refs/heads/bar \
+		HEAD:refs/for/master/topic \
+		HEAD:refs/for/next/topic \
+		>out 2>&1 &&
+	make_user_friendly_and_stable_output <out >actual &&
+	cat >expect <<-EOF &&
+	remote: # pre-receive hook
+	remote: pre-receive< <COMMIT-A> <COMMIT-B> refs/heads/bar
+	remote: pre-receive< <COMMIT-A> <ZERO-OID> refs/heads/foo
+	remote: pre-receive< <COMMIT-B> <COMMIT-A> refs/heads/master
+	remote: pre-receive< <ZERO-OID> <COMMIT-A> refs/for/master/topic
+	remote: pre-receive< <ZERO-OID> <COMMIT-A> refs/for/next/topic
+	remote: # proc-receive hook
+	remote: proc-receive< <COMMIT-A> <COMMIT-B> refs/heads/bar
+	remote: proc-receive< <COMMIT-A> <ZERO-OID> refs/heads/foo
+	remote: proc-receive< <COMMIT-B> <COMMIT-A> refs/heads/master
+	remote: proc-receive< <ZERO-OID> <COMMIT-A> refs/for/master/topic
+	remote: proc-receive< <ZERO-OID> <COMMIT-A> refs/for/next/topic
+	remote: proc-receive> ok refs/heads/master
+	remote: proc-receive> option fall-through
+	remote: proc-receive> ok refs/heads/foo
+	remote: proc-receive> option fall-through
+	remote: proc-receive> ok refs/heads/bar
+	remote: proc-receive> option fall-through
+	remote: proc-receive> ok refs/for/master/topic
+	remote: proc-receive> option refname refs/pull/123/head
+	remote: proc-receive> option old-oid <COMMIT-A>
+	remote: proc-receive> option new-oid <COMMIT-B>
+	remote: proc-receive> ok refs/for/next/topic
+	remote: proc-receive> option refname refs/pull/124/head
+	remote: proc-receive> option old-oid <COMMIT-B>
+	remote: proc-receive> option new-oid <COMMIT-A>
+	remote: proc-receive> option forced-update
+	remote: # post-receive hook
+	remote: post-receive< <COMMIT-A> <COMMIT-B> refs/heads/bar
+	remote: post-receive< <COMMIT-A> <ZERO-OID> refs/heads/foo
+	remote: post-receive< <COMMIT-B> <COMMIT-A> refs/heads/master
+	remote: post-receive< <COMMIT-A> <COMMIT-B> refs/pull/123/head
+	remote: post-receive< <COMMIT-B> <COMMIT-A> refs/pull/124/head
+	To <URL/of/upstream.git>
+	 <OID-A>..<OID-B> <COMMIT-B> -> bar
+	 - [deleted] foo
+	 + <OID-B>...<OID-A> HEAD -> master (forced update)
+	 <OID-A>..<OID-B> HEAD -> refs/pull/123/head
+	 + <OID-B>...<OID-A> HEAD -> refs/pull/124/head (forced update)
+	EOF
+	test_cmp expect actual &&
+	git -C "$upstream" show-ref >out &&
+	make_user_friendly_and_stable_output <out >actual &&
+	cat >expect <<-EOF &&
+	<COMMIT-B> refs/heads/bar
+	<COMMIT-A> refs/heads/baz
+	<COMMIT-A> refs/heads/master
+	EOF
+	test_cmp expect actual
+'
+
+# Refs of upstream : master(A)             bar(A)  baz(B)
+# Refs of workbench: master(A)  tags/v123
+test_expect_success "cleanup ($PROTOCOL)" '
+	(
+		cd "$upstream" &&
+		git update-ref -d refs/heads/bar &&
+		git update-ref -d refs/heads/baz
+	)
+'