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/t4048-diff-combined-binary.sh

@@ -9,24 +9,27 @@ test_expect_success 'setup binary merge conflict' '
 	git commit -m one &&
 	echo twoQ2 | q_to_nul >binary &&
 	git commit -a -m two &&
+	two=$(git rev-parse --short HEAD:binary) &&
 	git checkout -b branch-binary HEAD^ &&
 	echo threeQ3 | q_to_nul >binary &&
 	git commit -a -m three &&
+	three=$(git rev-parse --short HEAD:binary) &&
 	test_must_fail git merge master &&
 	echo resolvedQhooray | q_to_nul >binary &&
-	git commit -a -m resolved
+	git commit -a -m resolved &&
+	res=$(git rev-parse --short HEAD:binary)
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --git a/binary b/binary
-index 7ea6ded..9563691 100644
+index $three..$res 100644
 Binary files a/binary and b/binary differ
 resolved
 
 diff --git a/binary b/binary
-index 6197570..9563691 100644
+index $two..$res 100644
 Binary files a/binary and b/binary differ
 EOF
 test_expect_success 'diff -m indicates binary-ness' '
@@ -34,11 +37,11 @@ test_expect_success 'diff -m indicates binary-ness' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --combined binary
-index 7ea6ded,6197570..9563691
+index $three,$two..$res
 Binary files differ
 EOF
 test_expect_success 'diff -c indicates binary-ness' '
@@ -46,11 +49,11 @@ test_expect_success 'diff -c indicates binary-ness' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --cc binary
-index 7ea6ded,6197570..9563691
+index $three,$two..$res
 Binary files differ
 EOF
 test_expect_success 'diff --cc indicates binary-ness' '
@@ -62,23 +65,26 @@ test_expect_success 'setup non-binary with binary attribute' '
 	git checkout master &&
 	test_commit one text &&
 	test_commit two text &&
+	two=$(git rev-parse --short HEAD:text) &&
 	git checkout -b branch-text HEAD^ &&
 	test_commit three text &&
+	three=$(git rev-parse --short HEAD:text) &&
 	test_must_fail git merge master &&
 	test_commit resolved text &&
+	res=$(git rev-parse --short HEAD:text) &&
 	echo text -diff >.gitattributes
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --git a/text b/text
-index 2bdf67a..2ab19ae 100644
+index $three..$res 100644
 Binary files a/text and b/text differ
 resolved
 
 diff --git a/text b/text
-index f719efd..2ab19ae 100644
+index $two..$res 100644
 Binary files a/text and b/text differ
 EOF
 test_expect_success 'diff -m respects binary attribute' '
@@ -86,11 +92,11 @@ test_expect_success 'diff -m respects binary attribute' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --combined text
-index 2bdf67a,f719efd..2ab19ae
+index $three,$two..$res
 Binary files differ
 EOF
 test_expect_success 'diff -c respects binary attribute' '
@@ -98,11 +104,11 @@ test_expect_success 'diff -c respects binary attribute' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --cc text
-index 2bdf67a,f719efd..2ab19ae
+index $three,$two..$res
 Binary files differ
 EOF
 test_expect_success 'diff --cc respects binary attribute' '
@@ -115,11 +121,11 @@ test_expect_success 'setup textconv attribute' '
 	git config diff.upcase.textconv "tr a-z A-Z <"
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --git a/text b/text
-index 2bdf67a..2ab19ae 100644
+index $three..$res 100644
 --- a/text
 +++ b/text
 @@ -1 +1 @@
@@ -128,7 +134,7 @@ index 2bdf67a..2ab19ae 100644
 resolved
 
 diff --git a/text b/text
-index f719efd..2ab19ae 100644
+index $two..$res 100644
 --- a/text
 +++ b/text
 @@ -1 +1 @@
@@ -140,11 +146,11 @@ test_expect_success 'diff -m respects textconv attribute' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --combined text
-index 2bdf67a,f719efd..2ab19ae
+index $three,$two..$res
 --- a/text
 +++ b/text
 @@@ -1,1 -1,1 +1,1 @@@
@@ -157,11 +163,11 @@ test_expect_success 'diff -c respects textconv attribute' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 resolved
 
 diff --cc text
-index 2bdf67a,f719efd..2ab19ae
+index $three,$two..$res
 --- a/text
 +++ b/text
 @@@ -1,1 -1,1 +1,1 @@@
@@ -174,9 +180,9 @@ test_expect_success 'diff --cc respects textconv attribute' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 diff --combined text
-index 2bdf67a,f719efd..2ab19ae
+index $three,$two..$res
 --- a/text
 +++ b/text
 @@@ -1,1 -1,1 +1,1 @@@
@@ -190,9 +196,9 @@ test_expect_success 'diff-tree plumbing does not respect textconv' '
 	test_cmp expect actual
 '
 
-cat >expect <<'EOF'
+cat >expect <<EOF
 diff --cc text
-index 2bdf67a,f719efd..0000000
+index $three,$two..0000000
 --- a/text
 +++ b/text
 @@@ -1,1 -1,1 +1,5 @@@