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/t3201-branch-contains.sh

@@ -171,6 +171,69 @@ test_expect_success 'Assert that --contains only works on commits, not trees & b
 	test_must_fail git branch --no-contains $blob
 '
 
+test_expect_success 'multiple branch --contains' '
+	git checkout -b side2 master &&
+	>feature &&
+	git add feature &&
+	git commit -m "add feature" &&
+	git checkout -b next master &&
+	git merge side &&
+	git branch --contains side --contains side2 >actual &&
+	cat >expect <<-\EOF &&
+	* next
+	  side
+	  side2
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'multiple branch --merged' '
+	git branch --merged next --merged master >actual &&
+	cat >expect <<-\EOF &&
+	  master
+	* next
+	  side
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'multiple branch --no-contains' '
+	git branch --no-contains side --no-contains side2 >actual &&
+	cat >expect <<-\EOF &&
+	  master
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'multiple branch --no-merged' '
+	git branch --no-merged next --no-merged master >actual &&
+	cat >expect <<-\EOF &&
+	  side2
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'branch --contains combined with --no-contains' '
+	git checkout -b seen master &&
+	git merge side &&
+	git merge side2 &&
+	git branch --contains side --no-contains side2 >actual &&
+	cat >expect <<-\EOF &&
+	  next
+	  side
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'branch --merged combined with --no-merged' '
+	git branch --merged seen --no-merged next >actual &&
+	cat >expect <<-\EOF &&
+	* seen
+	  side2
+	EOF
+	test_cmp expect actual
+'
+
 # We want to set up a case where the walk for the tracking info
 # of one branch crosses the tip of another branch (and make sure
 # that the latter walk does not mess up our flag to see if it was
@@ -192,23 +255,12 @@ test_expect_success 'branch --merged with --verbose' '
 	EOF
 	test_cmp expect actual &&
 	git branch --verbose --merged topic >actual &&
-	cat >expect <<-\EOF &&
-	  master c77a0a9 second on master
-	* topic  2c939f4 [ahead 1] foo
-	  zzz    c77a0a9 second on master
+	cat >expect <<-EOF &&
+	  master $(git rev-parse --short master) second on master
+	* topic  $(git rev-parse --short topic ) [ahead 1] foo
+	  zzz    $(git rev-parse --short zzz   ) second on master
 	EOF
 	test_i18ncmp expect actual
 '
 
-test_expect_success 'branch --contains combined with --no-contains' '
-	git branch --contains zzz --no-contains topic >actual &&
-	cat >expect <<-\EOF &&
-	  master
-	  side
-	  zzz
-	EOF
-	test_cmp expect actual
-
-'
-
 test_done