set LC_TIME even if locale dir is not present

Since Commit aa1462c (introduce "format" date-mode, 2015-06-25) git log can pass
user specified format strings directly to strftime(). One special format string we
explicitly mention in our documentation is %c, which depends on the system locale.
To accommodate for %c we added a call to setlocale() in git_setup_gettext().

In Commit cc5e1bf (gettext: avoid initialization if the locale dir is not present,
2018-04-21) we added an early exit to git_setup_gettext() in case no textdomain
directory is present. This early exit is so early, that we don't even set the
locale for %c in that case, despite strftime() not needing the textdomain directory
at all.

This leads to a subtle bug where `git log --date=format:%c` will use C locale instead
of the system locale on systems without a valid textdomain directory.

This fixes git-for-windows#2959

Signed-off-by: Matthias Aßhauer <mha1993@live.de>

Author: rimrul

Makefile

@@ -410,6 +410,10 @@ include shared.mak
 # If it isn't set, fallback to $LC_ALL, $LANG or use the first utf-8
 # locale returned by "locale -a".
 #
+# Define GIT_TEST_TIME_LOCALE to preferred non-us locale for testing.
+# If it isn't set, fallback to $LC_ALL, $LANG or use the first non-us
+# locale returned by "locale -a".
+#
 # Define HAVE_CLOCK_GETTIME if your platform has clock_gettime.
 #
 # Define HAVE_CLOCK_MONOTONIC if your platform has CLOCK_MONOTONIC.
@@ -2862,6 +2866,9 @@ ifdef GIT_TEST_CMP_USE_COPIED_CONTEXT
 endif
 ifdef GIT_TEST_UTF8_LOCALE
 	@echo GIT_TEST_UTF8_LOCALE=\''$(subst ','\'',$(subst ','\'',$(GIT_TEST_UTF8_LOCALE)))'\' >>$@+
+endif
+ifdef GIT_TEST_TIME_LOCALE
+	@echo GIT_TEST_TIME_LOCALE=\''$(subst ','\'',$(subst ','\'',$(GIT_TEST_TIME_LOCALE)))'\' >>$@+
 endif
 	@echo NO_GETTEXT=\''$(subst ','\'',$(subst ','\'',$(NO_GETTEXT)))'\' >>$@+
 ifdef GIT_PERF_REPEAT_COUNT

gettext.c

@@ -107,6 +107,8 @@ void git_setup_gettext(void)
 	const char *podir = getenv(GIT_TEXT_DOMAIN_DIR_ENVIRONMENT);
 	char *p = NULL;
 
+	setlocale(LC_TIME, "");
+
 	if (!podir)
 		podir = p = system_path(GIT_LOCALE_PATH);
 
@@ -117,7 +119,6 @@ void git_setup_gettext(void)
 
 	bindtextdomain("git", podir);
 	setlocale(LC_MESSAGES, "");
-	setlocale(LC_TIME, "");
 	init_gettext_charset("git");
 	textdomain("git");
 

t/t4205-log-pretty-formats.sh

@@ -25,6 +25,29 @@ commit_msg () {
 	fi
 }
 
+prepare_time_locale () {
+	if test -z "$GIT_TEST_TIME_LOCALE"
+	then
+		case "${LC_ALL:-$LANG}" in
+		C | C.* | POSIX | POSIX.* | en_US | en_US.* )
+			GIT_TEST_TIME_LOCALE=$(locale -a | sed -n '/^\(C\|POSIX\|en_US\)/I !{
+				p
+				q
+			}')
+			;;
+		*)
+			GIT_TEST_TIME_LOCALE="${LC_ALL:-$LANG}"
+			;;
+		esac
+	fi
+	if test -n "$GIT_TEST_TIME_LOCALE"
+	then
+		test_set_prereq TIME_LOCALE
+	else
+		say "# No non-us locale available, some tests are skipped"
+	fi
+}
+
 test_expect_success 'set up basic repos' '
 	>foo &&
 	>bar &&
@@ -544,6 +567,14 @@ test_expect_success '--date=human %ad%cd is the same as %ah%ch' '
 	test_cmp expected actual
 '
 
+prepare_time_locale
+test_expect_success TIME_LOCALE '--date=format:%c does not need gettext' '
+	rm -fr no-such-dir &&
+	LC_ALL=$GIT_TEST_TIME_LOCALE git log --date=format:%c HEAD^1..HEAD >expected &&
+	GIT_TEXTDOMAINDIR=no-such-dir LC_ALL=$GIT_TEST_TIME_LOCALE git log --date=format:%c HEAD^1..HEAD >actual &&
+	test_cmp expected actual
+'
+
 # get new digests (with no abbreviations)
 test_expect_success 'set up log decoration tests' '
 	head1=$(git rev-parse --verify HEAD~0) &&