t9010: svnadmin can fail even if available

If svn is built against one version of SQLite and run against another,
libsvn_subr needlessly errors out in operations that need to make a
commit.

That is clearly not a bug in git but let us consider the ramifications for
the test suite.  git-svn uses libsvn directly and is probably broken by
that bug; it is right for git-svn tests to fail.  The vcs-svn lib, on the
other hand, does not use libsvn and the test t9010 only uses svn to check
its work.  This points to two possible improvements:

 - do not disable most vcs-svn tests if svn is missing.
 - skip validation rather than failing it when svn fails.

Bring about both by putting the svn invocations into a single test that
builds a repo to compare the test-svn-fe result against.  The test will
always pass but only will set the new SVNREPO test prereq if svn succeeds;
and validation using that repo gets an SVNREPO prerequisite so it only
runs with working svn installations.

Works-around: http://bugs.debian.org/608925
Noticed-by: A Large Angry SCM <gitzilla@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

t/t9010-svn-fe.sh

@@ -4,22 +4,6 @@ test_description='check svn dumpfile importer'
 
 . ./test-lib.sh
 
-if ! svnadmin -h >/dev/null 2>&1
-then
-	skip_all='skipping svn-fe tests, svn not available'
-	test_done
-fi
-
-svnconf=$PWD/svnconf
-export svnconf
-
-svn_cmd () {
-	subcommand=$1 &&
-	shift &&
-	mkdir -p "$svnconf" &&
-	svn "$subcommand" --config-dir "$svnconf" "$@"
-}
-
 reinit_git () {
 	rm -fr .git &&
 	git init
@@ -41,10 +25,21 @@ test_expect_success 'v3 dumps not supported' '
 	test_cmp empty stream
 '
 
-test_expect_success 't9135/svn.dump' '
-	svnadmin create simple-svn &&
-	svnadmin load simple-svn <"$TEST_DIRECTORY/t9135/svn.dump" &&
-	svn_cmd export "file://$PWD/simple-svn" simple-svnco &&
+test_expect_success 'set up svn repo' '
+	svnconf=$PWD/svnconf &&
+	mkdir -p "$svnconf" &&
+
+	if
+		svnadmin -h >/dev/null 2>&1 &&
+		svnadmin create simple-svn &&
+		svnadmin load simple-svn <"$TEST_DIRECTORY/t9135/svn.dump" &&
+		svn export --config-dir "$svnconf" "file://$PWD/simple-svn" simple-svnco
+	then
+		test_set_prereq SVNREPO
+	fi
+'
+
+test_expect_success SVNREPO 't9135/svn.dump' '
 	git init simple-git &&
 	test-svn-fe "$TEST_DIRECTORY/t9135/svn.dump" >simple.fe &&
 	(