Git svn migration does not work because fatal git checkout updating paths is incompatible with switching branches

[Christine Bauers <c.bauers@gmx.de>]

Hi there,

I´m trying to migrate a repository from svn to git which branches and 
tags with the following migration script:

git svn clone --no-metadata --stdlayout --A ../users.txt 
svn://host/svn/project/subproject subproject

cd subproject
git config svn.authorsfile ../../users.txt
git svn fetch

git checkout -b branch1 remotes/branch1
git checkout -b branch2 remotes/branch2
git checkout -b branch3 remotes/branch3

git checkout -b src_v1 remotes/tags/src
git checkout master
git tag src src_v1
git branch -D src_v1

git checkout -b WebContent_v1 remotes/tags/WebContent
git checkout master
git tag WebContent WebContent_v1
git branch -D WebContent_v1

and get the follwoing errors:

W: Ignoring error from SVN, path probably does not exist: (160013): 
Filesystem has no item: Datei nicht gefunden: Revision 8966, Pfad 
»subproject«
W: Do not be alarmed at the above message git-svn is just searching 
aggressively for old history.
This may take a while on large repositories
fatal: git checkout: updating paths is incompatible with switching branches.
Did you intend to checkout 'remotes/branch1' which can not be resolved 
as commit?
fatal: git checkout: updating paths is incompatible with switching branches.
Did you intend to checkout 'remotes/branch2 which can not be resolved as 
commit?
fatal: git checkout: updating paths is incompatible with switching branches.
Did you intend to checkout 'remotes/branch3' which can not be resolved 
as commit?
fatal: git checkout: updating paths is incompatible with switching branches.
Did you intend to checkout 'remotes/tags/src' which can not be resolved 
as commit?
error: pathspec 'master' did not match any file(s) known to git.
fatal: Failed to resolve 'src_v1' as a valid ref.
error: branch 'src_v1' not found.
fatal: git checkout: updating paths is incompatible with switching branches.
Did you intend to checkout 'remotes/tags/WebContent' which can not be 
resolved as commit?
error: pathspec 'master' did not match any file(s) known to git.
fatal: Failed to resolve 'WebContent_v1' as a valid ref.
error: branch 'WebContent_v1' not found.

How do I solve this problem?

Greetings
Christine