Merge branch 'nd/trace-with-env'

The tracing machinery learned to report tweaking of environment
variables as well.

* nd/trace-with-env:
  run-command.c: print new cwd in trace_run_command()
  run-command.c: print env vars in trace_run_command()
  run-command.c: print program 'git' when tracing git_cmd mode
  run-command.c: introduce trace_run_command()
  trace.c: move strbuf_release() out of print_trace_line()
  trace: avoid unnecessary quoting
  sq_quote_argv: drop maxlen parameter