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
# In the merge below, the file "foo" has the same contents in both
# parents, but if we look at the file-level history, we'll notice that
# the version in p1 is an ancestor of the version in p2. This test
# makes sure that we'll use the version from p2 in the manifest of the
# merge revision.
hg init repo
cd repo
echo foo > foo
hg ci -d '0 0' -qAm 'add foo'
echo bar >> foo
hg ci -d '0 0' -m 'change foo'
hg backout -d '0 0' -r tip -m 'backout changed foo'
hg up -C 0
touch bar
hg ci -d '0 0' -qAm 'add bar'
hg merge --debug
hg debugstate | grep foo
hg st -A foo
hg ci -d '0 0' -m 'merge'
hg manifest --debug | grep foo
hg debugindex .hg/store/data/foo.i