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/perf/p5310-pack-bitmaps.sh

@@ -31,14 +31,37 @@ test_perf 'simulated fetch' '
 	} | git pack-objects --revs --stdout >/dev/null
 '
 
-test_perf 'pack to file' '
-	git pack-objects --all pack1 </dev/null >/dev/null
-'
-
 test_perf 'pack to file (bitmap)' '
 	git pack-objects --use-bitmap-index --all pack1b </dev/null >/dev/null
 '
 
+test_perf 'rev-list (commits)' '
+	git rev-list --all --use-bitmap-index >/dev/null
+'
+
+test_perf 'rev-list (objects)' '
+	git rev-list --all --use-bitmap-index --objects >/dev/null
+'
+
+test_perf 'rev-list count with blob:none' '
+	git rev-list --use-bitmap-index --count --objects --all \
+		--filter=blob:none >/dev/null
+'
+
+test_perf 'rev-list count with blob:limit=1k' '
+	git rev-list --use-bitmap-index --count --objects --all \
+		--filter=blob:limit=1k >/dev/null
+'
+
+test_perf 'rev-list count with tree:0' '
+	git rev-list --use-bitmap-index --count --objects --all \
+		--filter=tree:0 >/dev/null
+'
+
+test_perf 'simulated partial clone' '
+	git pack-objects --stdout --all --filter=blob:none </dev/null >/dev/null
+'
+
 test_expect_success 'create partial bitmap state' '
 	# pick a commit to represent the repo tip in the past
 	cutoff=$(git rev-list HEAD~100 -1) &&
@@ -68,4 +91,9 @@ test_perf 'pack to file (partial bitmap)' '
 	git pack-objects --use-bitmap-index --all pack2b </dev/null >/dev/null
 '
 
+test_perf 'rev-list with tree filter (partial bitmap)' '
+	git rev-list --use-bitmap-index --count --objects --all \
+		--filter=tree:0 >/dev/null
+'
+
 test_done