Merge branch 'ab/hook-api-with-stdin'

Extend the run-hooks API to allow feeding data from the standard input when running the hook script(s). * ab/hook-api-with-stdin: hook: support a --to-stdin=<path> option sequencer: use the new hook API for the simpler "post-rewrite" call hook API: support passing stdin to hooks, convert am's 'post-rewrite' run-command: allow stdin for run_processes_parallel run-command.c: remove dead assignment in while-loop