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/t4210-log-i18n.sh

@@ -1,12 +1,22 @@
 #!/bin/sh
 
 test_description='test log with i18n features'
-. ./test-lib.sh
+. ./lib-gettext.sh
 
 # two forms of é
 utf8_e=$(printf '\303\251')
 latin1_e=$(printf '\351')
 
+# invalid UTF-8
+invalid_e=$(printf '\303\50)') # ")" at end to close opening "("
+
+have_reg_illseq=
+if test_have_prereq GETTEXT_LOCALE &&
+	! LC_ALL=$is_IS_locale test-tool regex --silent $latin1_e
+then
+	have_reg_illseq=1
+fi
+
 test_expect_success 'create commits in different encodings' '
 	test_tick &&
 	cat >msg <<-EOF &&
@@ -53,4 +63,72 @@ test_expect_success 'log --grep does not find non-reencoded values (latin1)' '
 	test_must_be_empty actual
 '
 
+triggers_undefined_behaviour () {
+	local engine=$1
+
+	case $engine in
+	fixed)
+		if test -n "$have_reg_illseq" &&
+			! test_have_prereq LIBPCRE2
+		then
+			return 0
+		fi
+		;;
+	basic|extended)
+		if test -n "$have_reg_illseq"
+		then
+			return 0
+		fi
+		;;
+	esac
+	return 1
+}
+
+mismatched_git_log () {
+	local pattern=$1
+
+	LC_ALL=$is_IS_locale git log --encoding=ISO-8859-1 --format=%s \
+		--grep=$pattern
+}
+
+for engine in fixed basic extended perl
+do
+	prereq=
+	if test $engine = "perl"
+	then
+		prereq=PCRE
+	fi
+	force_regex=
+	if test $engine != "fixed"
+	then
+		force_regex='.*'
+	fi
+
+	test_expect_success $prereq "config grep.patternType=$engine" "
+		git config grep.patternType $engine
+	"
+
+	test_expect_success GETTEXT_LOCALE,$prereq "log --grep does not find non-reencoded values (latin1 + locale)" "
+		mismatched_git_log '$force_regex$utf8_e' >actual &&
+		test_must_be_empty actual
+	"
+
+	if ! triggers_undefined_behaviour $engine
+	then
+		test_expect_success !MINGW,GETTEXT_LOCALE,$prereq "log --grep searches in log output encoding (latin1 + locale)" "
+			cat >expect <<-\EOF &&
+			latin1
+			utf8
+			EOF
+			mismatched_git_log '$force_regex$latin1_e' >actual &&
+			test_cmp expect actual
+		"
+
+		test_expect_success GETTEXT_LOCALE,$prereq "log --grep does not die on invalid UTF-8 value (latin1 + locale + invalid needle)" "
+			mismatched_git_log '$force_regex$invalid_e' >actual &&
+			test_must_be_empty actual
+		"
+	fi
+done
+
 test_done