Don't try to determine interactivity if ui() called with interactive=False.
WSGI applications are not supposed to refer to sys.stdin. In ed6df6b1c29a,
hgweb and hgwebdir were fixed to pass interactive=False to their ui()'s, but
sys.stdin.isatty() was still called by the ui objects. This change makes sure
only the ui.fixconfig() method will call ui.isatty() (by making the
ui._readline() method, which is currently only called from ui.prompt(),
private). ui.fixconfig() is changed to let config files override the initial
interactivity setting, but not check isatty() if interactive=False was
specified in the creation of the ui.
#!/bin/sh
mkdir t
cd t
hg init
mkdir a
echo foo > a/a
echo bar > a/b
hg add a
hg ci -m "0" -d "0 0"
hg co -C 0
hg mv a b
hg ci -m "1 mv a/ b/" -d "0 0"
hg co -C 0
echo baz > a/c
hg add a/c
hg ci -m "2 add a/c" -d "0 0"
hg merge --debug 1
echo a/* b/*
hg st -C
hg ci -m "3 merge 2+1" -d "0 0"
hg debugrename b/c
hg co -C 1
hg merge --debug 2
echo a/* b/*
hg st -C
hg ci -m "4 merge 1+2" -d "0 0"
hg debugrename b/c