t9350: skip ISO-8859-? tests when the environment is always-UTF-8

In the BusyBox-w32 version that is currently under consideration for
MinGit for Windows (to reduce the .zip size, and to avoid problems with
the MSYS2 runtime), the UTF-16 environment present in Windows is
considered to be authoritative, and the 8-bit version is always in UTF-8
encoding.

As a consequence, the ISO-8859-? tests in t9350-fast-export (which try
to set GIT_AUTHOR_NAME to a ISO-8859-? encoded value) *must* fail in
that setup.

So let's detect when they would fail (due to an environment being purely
kept UTF-8 encoded), and skip those tests in that case.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

t/t9350-fast-export.sh

@@ -94,7 +94,12 @@ test_expect_success 'fast-export --show-original-ids | git fast-import' '
 	test $MUSS = $(git rev-parse --verify refs/tags/muss)
 '
 
-test_expect_success 'reencoding iso-8859-7' '
+test_lazy_prereq UTF8_ONLY_ENV '
+	. "$TEST_DIRECTORY"/t3901/8859-1.txt &&
+	! git var GIT_AUTHOR_IDENT | grep "Áéí"
+'
+
+test_expect_success !UTF8_ONLY_ENV 'reencoding iso-8859-7' '
 
 	test_when_finished "git reset --hard HEAD~1" &&
 	test_config i18n.commitencoding iso-8859-7 &&
@@ -109,7 +114,7 @@ test_expect_success 'reencoding iso-8859-7' '
 		 grep $(printf "\317\200") actual)
 '
 
-test_expect_success 'aborting on iso-8859-7' '
+test_expect_success !UTF8_ONLY_ENV 'aborting on iso-8859-7' '
 
 	test_when_finished "git reset --hard HEAD~1" &&
 	test_config i18n.commitencoding iso-8859-7 &&
@@ -118,7 +123,7 @@ test_expect_success 'aborting on iso-8859-7' '
 	test_must_fail git fast-export --reencode=abort wer^..wer >iso-8859-7.fi
 '
 
-test_expect_success 'preserving iso-8859-7' '
+test_expect_success !UTF8_ONLY_ENV 'preserving iso-8859-7' '
 
 	test_when_finished "git reset --hard HEAD~1" &&
 	test_config i18n.commitencoding iso-8859-7 &&
@@ -132,7 +137,7 @@ test_expect_success 'preserving iso-8859-7' '
 		 grep $(printf "\360") actual)
 '
 
-test_expect_success 'encoding preserved if reencoding fails' '
+test_expect_success !UTF8_ONLY_ENV 'encoding preserved if reencoding fails' '
 
 	test_when_finished "git reset --hard HEAD~1" &&
 	test_config i18n.commitencoding iso-8859-7 &&
@@ -146,6 +151,10 @@ test_expect_success 'encoding preserved if reencoding fails' '
 		 grep ^encoding actual)
 '
 
+# The subsequent tests validate timestamps, and we may just have skipped a tick
+test_have_prereq !UTF8_ONLY_ENV ||
+test_tick
+
 test_expect_success 'import/export-marks' '
 
 	git checkout -b marks master &&