mingw: avoid illegal filename in t9118

On Windows' file systems, file names with trailing dots are forbidden.
The POSIX emulation layer used by Git for Windows' Subversion emulates
those file names, therefore the test adding the file would actually
succeed, but when we would ask git.exe (which does not leverage the
POSIX emulation layer) to check out the tree, it would fail.

Let's just guard the test using a filename that is illegal on Windows
by the MINGW prereq.

This lets t9118-git-svn-funky-branch-names.sh pass in Git for Windows'
SDK.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t9118-git-svn-funky-branch-names.sh

@@ -23,8 +23,11 @@ test_expect_success 'setup svnrepo' '
 	              "$svnrepo/pr ject/branches/$scary_uri" &&
 	svn_cmd cp -m "leading dot" "$svnrepo/pr ject/trunk" \
 			"$svnrepo/pr ject/branches/.leading_dot" &&
-	svn_cmd cp -m "trailing dot" "$svnrepo/pr ject/trunk" \
-			"$svnrepo/pr ject/branches/trailing_dot." &&
+	if test_have_prereq !MINGW
+	then
+		svn_cmd cp -m "trailing dot" "$svnrepo/pr ject/trunk" \
+			"$svnrepo/pr ject/branches/trailing_dot."
+	fi &&
 	svn_cmd cp -m "trailing .lock" "$svnrepo/pr ject/trunk" \
 			"$svnrepo/pr ject/branches/trailing_dotlock.lock" &&
 	svn_cmd cp -m "reflog" "$svnrepo/pr ject/trunk" \
@@ -45,7 +48,10 @@ test_expect_success 'test clone with funky branch names' '
 		git rev-parse "refs/remotes/origin/more%20fun%20plugin!" &&
 		git rev-parse "refs/remotes/origin/$scary_ref" &&
 		git rev-parse "refs/remotes/origin/%2Eleading_dot" &&
-		git rev-parse "refs/remotes/origin/trailing_dot%2E" &&
+		if test_have_prereq !MINGW
+		then
+			git rev-parse "refs/remotes/origin/trailing_dot%2E"
+		fi &&
 		git rev-parse "refs/remotes/origin/trailing_dotlock%2Elock" &&
 		git rev-parse "refs/remotes/origin/$non_reflog"
 	)