Lynn Lin [off-list ref] writes:

When I create a local branch and then push it to remote. I find that
the output without error goes into stderr, is this expected?

Progress output are sent to the stderr stream.

In general, any program or script is buggy if it assumes that some output
that are emitted to the standard error output from programs it invokes
indicates an error (IIRC, that includes tcl/tk).