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/t0212-trace2-event.sh

@@ -199,6 +199,43 @@ test_expect_success JSON_PP 'event stream, list config' '
 	test_cmp expect actual
 '
 
+# Test listing of all "interesting" environment variables.
+
+test_expect_success JSON_PP 'event stream, list env vars' '
+	test_when_finished "rm trace.event actual expect" &&
+	GIT_TRACE2_EVENT="$(pwd)/trace.event" \
+		GIT_TRACE2_ENV_VARS="A_VAR,OTHER_VAR,MISSING" \
+		A_VAR=1 OTHER_VAR="hello world" test-tool trace2 001return 0 &&
+	perl "$TEST_DIRECTORY/t0212/parse_events.perl" <trace.event >actual &&
+	sed -e "s/^|//" >expect <<-EOF &&
+	|VAR1 = {
+	|  "_SID0_":{
+	|    "argv":[
+	|      "_EXE_",
+	|      "trace2",
+	|      "001return",
+	|      "0"
+	|    ],
+	|    "exit_code":0,
+	|    "hierarchy":"trace2",
+	|    "name":"trace2",
+	|    "params":[
+	|      {
+	|        "param":"A_VAR",
+	|        "value":"1"
+	|      },
+	|      {
+	|        "param":"OTHER_VAR",
+	|        "value":"hello world"
+	|      }
+	|    ],
+	|    "version":"$V"
+	|  }
+	|};
+	EOF
+	test_cmp expect actual
+'
+
 test_expect_success JSON_PP 'basic trace2_data' '
 	test_when_finished "rm trace.event actual expect" &&
 	GIT_TRACE2_EVENT="$(pwd)/trace.event" test-tool trace2 006data test_category k1 v1 test_category k2 v2 &&
@@ -265,4 +302,23 @@ test_expect_success JSON_PP 'using global config, event stream, error event' '
 	test_cmp expect actual
 '
 
+test_expect_success 'discard traces when there are too many files' '
+	mkdir trace_target_dir &&
+	test_when_finished "rm -r trace_target_dir" &&
+	(
+		GIT_TRACE2_MAX_FILES=5 &&
+		export GIT_TRACE2_MAX_FILES &&
+		cd trace_target_dir &&
+		test_seq $GIT_TRACE2_MAX_FILES >../expected_filenames.txt &&
+		xargs touch <../expected_filenames.txt &&
+		cd .. &&
+		GIT_TRACE2_EVENT="$(pwd)/trace_target_dir" test-tool trace2 001return 0
+	) &&
+	echo git-trace2-discard >>expected_filenames.txt &&
+	ls trace_target_dir >ls_output.txt &&
+	test_cmp expected_filenames.txt ls_output.txt &&
+	head -n1 trace_target_dir/git-trace2-discard | grep \"event\":\"version\" &&
+	head -n2 trace_target_dir/git-trace2-discard | tail -n1 | grep \"event\":\"too_many_files\"
+'
+
 test_done