Merge branch 'jk/pipe-command-nonblock' into maint

Fix deadlocks between main Git process and subprocess spawned via the pipe_command() API, that can kill "git add -p" that was reimplemented in C recently. * jk/pipe-command-nonblock: pipe_command(): mark stdin descriptor as non-blocking pipe_command(): handle ENOSPC when writing to a pipe pipe_command(): avoid xwrite() for writing to pipe git-compat-util: make MAX_IO_SIZE define globally available nonblock: support Windows compat: add function to enable nonblocking pipes