The man page says

         [src/linux-2.6]
         checkout = git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git &&
               cd linux-2.6 &&
               git checkout -b mybranch origin/master

       The .mrconfig file uses a variant of the INI file format. Lines
       starting with "#" are comments. Values can be continued to the
       following line by indenting the line with whitespace.

But this apparently only works if the shell also accepts line
continuations at the respective place.  This, for example, won't work:

         [src/linux-2.6]
         checkout = git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
               && cd linux-2.6
               && git checkout -b mybranch origin/master

$ mr up
mr checkout: /home/peter/tmp/src/linux-2.6
sh: 48: Syntax error: "&&" unexpected
mr checkout: command failed

Putting backslashes at the end of the lines, as in the shell, does
work.

Either the documentation should be clarified about this, or perhaps
the actual implementation should be tweaked to support the advertised
behavior.

Hi Richard,

in case this bug report did not reach you, I wanted to briefly follow
up.

I would be very happy to help with a migration of the package from
branchable.com to salsa.debian.org. Since this is a Debian native
package, hosting it on Salsa seems like a natural fit. Noting your
involvement with the git-annex and zsh maintainer teams on Salsa, I
assume the platform itself is not an obstacle for you.

If this is mainly a matter of time or capacity, I'm glad to assist with
the migration work.

If you would prefer not to move the repository, it would be helpful if
you could tag the bug as wontfix. In that case, an upload of the current
Git state would still be very welcome, as it would allow closing two
open bugs (#685002, #1105038) and improve dgit support.

Thanks for your time, and please let me know how you'd like to proceed.

Thank you for considering
   Andreas.