[PATCH v3 3/3] t: restrict `is_hidden` to be called only on Windows

["Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>]

From: Johannes Schindelin <johannes.schindelin@gmx.de>

The function won't work anywhere else, so let's mark it as an explicit
bug if it is called on a non-Windows platform.

Let's also rename the function to avoid cluttering the global namespace
with an overly-generic function name.

While at it, we also fix the code comment above that function: the
lower-case `windows` refers to something different than `Windows`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 t/t0001-init.sh         | 2 +-
 t/t5611-clone-config.sh | 6 +++---
 t/test-lib-functions.sh | 7 +++++--
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/t/t0001-init.sh b/t/t0001-init.sh
index 9cc919d8d1a..1edd5aeb8f0 100755
--- a/t/t0001-init.sh
+++ b/t/t0001-init.sh
@@ -399,7 +399,7 @@ test_expect_success MINGW '.git hidden' '
 		mkdir newdir &&
 		cd newdir &&
 		git init &&
-		is_hidden .git
+		test_path_is_hidden .git
 	) &&
 	check_config newdir/.git false unset
 '
diff --git a/t/t5611-clone-config.sh b/t/t5611-clone-config.sh
index c861e12ea44..8e0fd398236 100755
--- a/t/t5611-clone-config.sh
+++ b/t/t5611-clone-config.sh
@@ -96,13 +96,13 @@ test_expect_success MINGW 'clone -c core.hideDotFiles' '
 	test_commit attributes .gitattributes "" &&
 	rm -rf child &&
 	git clone -c core.hideDotFiles=false . child &&
-	! is_hidden child/.gitattributes &&
+	! test_path_is_hidden child/.gitattributes &&
 	rm -rf child &&
 	git clone -c core.hideDotFiles=dotGitOnly . child &&
-	! is_hidden child/.gitattributes &&
+	! test_path_is_hidden child/.gitattributes &&
 	rm -rf child &&
 	git clone -c core.hideDotFiles=true . child &&
-	is_hidden child/.gitattributes
+	test_path_is_hidden child/.gitattributes
 '
 
 test_done
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 2f81463a240..139647a6341 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1544,8 +1544,11 @@ test_bitmap_traversal () {
 	rm -f "$1.normalized" "$2.normalized"
 }
 
-# Tests for the hidden file attribute on windows
-is_hidden () {
+# Tests for the hidden file attribute on Windows
+test_path_is_hidden () {
+	test_have_prereq MINGW ||
+	BUG "test_path_is_hidden can only be used on Windows"
+
 	# Use the output of `attrib`, ignore the absolute path
 	case "$("$SYSTEMROOT"/system32/attrib "$1")" in *H*?:*) return 0;; esac
 	return 1
-- 
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