If using --log or -j > 1, disable stdin.

Parallelism and redo-log cause lots of confusion for any rules that try
to ask the user for questions, so disable it altogether.

Arguably, we should just disable stdin all the time, but maybe it's
still occasionally useful (even though you have to pass --no-log to get
it back).

Documentation/redo.md

@@ -38,6 +38,11 @@ instead.
 A .do script can call redo recursively to build its
 dependencies.
 
+To avoid confusion caused by multiple programs trying to
+use the terminal, inside .do scripts, stdin is normally
+redirected to /dev/null.  The only exception is if the `-j`
+option is *not* given and `--no-log` is used.
+
 
 # OPTIONS
 

builder.py

@@ -22,9 +22,14 @@ def _try_stat(filename):
 log_reader_pid = None
 
 
+def close_stdin():
+    f = open('/dev/null')
+    os.dup2(f.fileno(), 0)
+    f.close()
+
+
 def start_stdin_log_reader(status, details, pretty, color,
                            debug_locks, debug_pids):
-    if not vars.LOG: return
     global log_reader_pid
     r, w = os.pipe()    # main pipe to redo-log
     ar, aw = os.pipe()  # ack pipe from redo-log --ack-fd

redo-ifchange.py

@@ -19,7 +19,8 @@ def should_build(t):
 
 rv = 202
 try:
-    if vars_init.is_toplevel:
+    if vars_init.is_toplevel and vars.LOG:
+        builder.close_stdin()
         builder.start_stdin_log_reader(status=True, details=True,
             pretty=True, color=True, debug_locks=False, debug_pids=False)
     if vars.TARGET and not vars.UNLOCKED:

redo.py

@@ -79,7 +79,10 @@ import vars, state, builder, jwack
 from logs import warn, err
 
 try:
-    if vars_init.is_toplevel:
+    j = atoi(opt.jobs or 1)
+    if vars_init.is_toplevel and (vars.LOG or j > 1):
+        builder.close_stdin()
+    if vars_init.is_toplevel and vars.LOG:
         builder.start_stdin_log_reader(status=opt.status, details=opt.details,
             pretty=opt.pretty, color=opt.color,
             debug_locks=opt.debug_locks, debug_pids=opt.debug_pids)
@@ -91,7 +94,6 @@ try:
                      % f.nicename())
     state.rollback()
     
-    j = atoi(opt.jobs or 1)
     if j < 1 or j > 1000:
         err('invalid --jobs value: %r\n' % opt.jobs)
     jwack.setup(j)