I have installed "topgit" from nixpkgs (as described at http://nixos.org/nix/ : curl https://nixos.org/nix/install | sh ; make sure that ~/.nix-profile/bin is in your PATH -- .bash_profile gets updated by the installation procedure; nix-env -i topgit).
In eshell, it doesn't work:
$ ~/.nix-profile/bin/tg create example-simple_/essence
/nix/store/cxrc12hkmvrjlq747cm08av6jl41nzi1-bash-4.3-p30/bin/sh: : No such file or directory
In a normal terminal with shell, it works.
Also, the following works successfully in eshell, too:
$ strace -e trace=file -fF ~/.nix-profile/bin/tg create example-simple_/essence
It seems that I catched a similar bug in eshell a long time ago: once I couldn't successfully finish an "rpm -ba ..." build process in eshell (or "gear-hsh").
I had a guess that it's caused by broken signal handling or child process management in eshell...
(I want to file this bug report under Sisyphus after I check that the bug appears in the Sisyphus release of emacs, too.)