git-svn: handle empty files marked as symlinks in SVN

Broken SVN clients generate empty files with the svn:special set
to '*'.  This attempts to denote a symlink pointing to a file
with an empty path (""), which cannot be generated on a POSIX
system.

Thus, we mimic the behavior of svn(1) and create a zero-byte
file in our tree.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

t/t9131-git-svn-empty-symlink.sh

@@ -0,0 +1,90 @@
+#!/bin/sh
+
+test_description='test that git handles an svn repository with empty symlinks'
+
+. ./lib-git-svn.sh
+test_expect_success 'load svn dumpfile' '
+	svnadmin load "$rawsvnrepo" <<EOF
+SVN-fs-dump-format-version: 2
+
+UUID: 60780f9a-7df5-43b4-83ab-60e2c0673ef7
+
+Revision-number: 0
+Prop-content-length: 56
+Content-length: 56
+
+K 8
+svn:date
+V 27
+2008-11-26T07:17:27.590577Z
+PROPS-END
+
+Revision-number: 1
+Prop-content-length: 111
+Content-length: 111
+
+K 7
+svn:log
+V 4
+test
+K 10
+svn:author
+V 12
+normalperson
+K 8
+svn:date
+V 27
+2008-11-26T07:18:03.511836Z
+PROPS-END
+
+Node-path: bar
+Node-kind: file
+Node-action: add
+Prop-content-length: 33
+Text-content-length: 0
+Text-content-md5: d41d8cd98f00b204e9800998ecf8427e
+Content-length: 33
+
+K 11
+svn:special
+V 1
+*
+PROPS-END
+
+Revision-number: 2
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 13
+bar => doink
+
+K 10
+svn:author
+V 12
+normalperson
+K 8
+svn:date
+V 27
+2008-11-27T03:55:31.601672Z
+PROPS-END
+
+Node-path: bar
+Node-kind: file
+Node-action: change
+Text-content-length: 10
+Text-content-md5: 92ca4fe7a9721f877f765c252dcd66c9
+Content-length: 10
+
+link doink
+
+EOF
+'
+
+test_expect_success 'clone using git svn' 'git svn clone -r1 "$svnrepo" x'
+test_expect_success '"bar" is an empty file' 'test -f x/bar && ! test -s x/bar'
+test_expect_success 'get "bar" => symlink fix from svn' \
+		'(cd x && git svn rebase)'
+test_expect_success '"bar" becomes a symlink' 'test -L x/bar'
+test_done