# HG changeset patch
# User Augie Fackler <augie@google.com>
# Date 1473821877 14400
# Node ID e1f0ec0b7d2d1f555c7f3f506f8644185d081737
# Parent  285a8c3e53f2183438f0cdbc238e4ab851d0d110
flags: allow specifying --no-boolean-flag on the command line (BC)

This makes it much easier to enable some anti-foot-shooting features
(like update --check) by default, because now all boolean flags can be
explicitly disabled on the command line without having to use HGPLAIN
or similar. Flags which don't deserve this treatment can be removed
from consideration by adding them to the nevernegate set in fancyopts.

This doesn't make it any easier to identify when a flag is set: opts
still always gets filled in, either with the user-specified flag value
or with the default from the flags list in the command
table. Improving that would probably clean things up a bit, but for
now if you want a boolean flag and care if it was explicitly false or
default false (or true, but nobody uses that functionality because
before now it was nonsense) you need to use None as your default
rather than True or False.

This doesn't (yet) update help output, because I'm not quite sure how
to do that cleanly.

diff -r 285a8c3e53f2 -r e1f0ec0b7d2d mercurial/fancyopts.py
--- a/mercurial/fancyopts.py	Tue May 03 13:36:12 2016 +0900
+++ b/mercurial/fancyopts.py	Tue Sep 13 22:57:57 2016 -0400
@@ -12,6 +12,17 @@
 from .i18n import _
 from . import error
 
+# Set of flags to not apply boolean negation logic on
+nevernegate = set([
+    # avoid --no-noninteractive
+    'noninteractive',
+    # These two flags are special because they cause hg to do one
+    # thing and then exit, and so aren't suitable for use in things
+    # like aliases anyway.
+    'help',
+    'version',
+    ])
+
 def gnugetopt(args, options, longoptions):
     """Parse options mostly like getopt.gnu_getopt.
 
@@ -64,6 +75,8 @@
     shortlist = ''
     argmap = {}
     defmap = {}
+    negations = {}
+    alllong = set(o[1] for o in options)
 
     for option in options:
         if len(option) == 5:
@@ -91,6 +104,18 @@
                 short += ':'
             if oname:
                 oname += '='
+        elif oname not in nevernegate:
+            if oname.startswith('no-'):
+                insert = oname[3:]
+            else:
+                insert = 'no-' + oname
+            # backout (as a practical example) has both --commit and
+            # --no-commit options, so we don't want to allow the
+            # negations of those flags.
+            if insert not in alllong:
+                assert ('--' + oname) not in negations
+                negations['--' + insert] = '--' + oname
+                namelist.append(insert)
         if short:
             shortlist += short
         if name:
@@ -105,6 +130,11 @@
 
     # transfer result to state
     for opt, val in opts:
+        boolval = True
+        negation = negations.get(opt, False)
+        if negation:
+            opt = negation
+            boolval = False
         name = argmap[opt]
         obj = defmap[name]
         t = type(obj)
@@ -121,7 +151,7 @@
         elif t is type([]):
             state[name].append(val)
         elif t is type(None) or t is type(False):
-            state[name] = True
+            state[name] = boolval
 
     # return unparsed args
     return args
diff -r 285a8c3e53f2 -r e1f0ec0b7d2d tests/test-update-branches.t
--- a/tests/test-update-branches.t	Tue May 03 13:36:12 2016 +0900
+++ b/tests/test-update-branches.t	Tue Sep 13 22:57:57 2016 -0400
@@ -379,3 +379,14 @@
 
   $ hg log -r '_destupdate()'
   2:bd10386d478c 2 (no-eol)
+
+Test that boolean flags allow --no-flag specification to override [defaults]
+  $ cat >> $HGRCPATH <<EOF
+  > [defaults]
+  > update = --check
+  > EOF
+  $ hg co 2
+  abort: uncommitted changes
+  [255]
+  $ hg co --no-check 2
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved