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/t3406-rebase-message.sh

@@ -18,32 +18,29 @@ test_expect_success 'setup' '
 '
 
 test_expect_success 'rebase -m' '
-	git rebase -m master >report &&
-	>expect &&
-	sed -n -e "/^Already applied: /p" \
-		-e "/^Committed: /p" report >actual &&
-	test_cmp expect actual
+	git rebase -m master >actual &&
+	test_must_be_empty actual
 '
 
 test_expect_success 'rebase against master twice' '
-	git rebase master >out &&
+	git rebase --apply master >out &&
 	test_i18ngrep "Current branch topic is up to date" out
 '
 
 test_expect_success 'rebase against master twice with --force' '
-	git rebase --force-rebase master >out &&
+	git rebase --force-rebase --apply master >out &&
 	test_i18ngrep "Current branch topic is up to date, rebase forced" out
 '
 
 test_expect_success 'rebase against master twice from another branch' '
 	git checkout topic^ &&
-	git rebase master topic >out &&
+	git rebase --apply master topic >out &&
 	test_i18ngrep "Current branch topic is up to date" out
 '
 
 test_expect_success 'rebase fast-forward to master' '
 	git checkout topic^ &&
-	git rebase topic >out &&
+	git rebase --apply topic >out &&
 	test_i18ngrep "Fast-forwarded HEAD to topic" out
 '
 
@@ -95,9 +92,9 @@ test_expect_success 'GIT_REFLOG_ACTION' '
 	git rebase reflog-onto &&
 	git log -g --format=%gs -3 >actual &&
 	cat >expect <<-\EOF &&
-	rebase finished: returning to refs/heads/reflog-topic
-	rebase: reflog-to-rebase
-	rebase: checkout reflog-onto
+	rebase (finish): returning to refs/heads/reflog-topic
+	rebase (pick): reflog-to-rebase
+	rebase (start): checkout reflog-onto
 	EOF
 	test_cmp expect actual &&
 
@@ -105,9 +102,9 @@ test_expect_success 'GIT_REFLOG_ACTION' '
 	GIT_REFLOG_ACTION=change-the-reflog git rebase reflog-onto &&
 	git log -g --format=%gs -3 >actual &&
 	cat >expect <<-\EOF &&
-	rebase finished: returning to refs/heads/reflog-prefix
-	change-the-reflog: reflog-to-rebase
-	change-the-reflog: checkout reflog-onto
+	change-the-reflog (finish): returning to refs/heads/reflog-prefix
+	change-the-reflog (pick): reflog-to-rebase
+	change-the-reflog (start): checkout reflog-onto
 	EOF
 	test_cmp expect actual
 '