* Add a --autounmask[=n] option and for now leave it disable

by default in order to minimize the impact of any bugs.
* If _wrapped_select_pkg_highest_available_imp returns an installed
package when the user has not explicitly requested for this package
to be replaced (typically via an atom on the command line), reject
the installed package and try to unmask one.

4 files changed, 62 insertions, 6 deletions

diff --git a/man/emerge.1 b/man/emerge.1
index 572002d3d..73c90d3fd 100644
--- a/man/emerge.1
+++ b/man/emerge.1
@@ -284,6 +284,15 @@ acceptance of the first choice. This option is
 intended to be set in the \fBmake.conf\fR(5)
 \fBEMERGE_DEFAULT_OPTS\fR variable.
 .TP
+.BR "\-\-autounmask[=n]"
+Automatically unmask packages. If any configuration
+changes are required, then they will be displayed
+after the merge list and emerge will immediately
+abort. If the displayed configuration changes are
+satisfactory, you should copy and paste them into
+the specified configuration file(s). Currently,
+this only works for unstable KEYWORDS masks.
+.TP
 .BR \-\-backtrack=COUNT
 Specifies an integer number of times to backtrack if
 dependency calculation fails due to a conflict or an
diff --git a/pym/_emerge/depgraph.py b/pym/_emerge/depgraph.py
index 056c7bdb5..05c108592 100644
--- a/pym/_emerge/depgraph.py
+++ b/pym/_emerge/depgraph.py
@@ -2483,15 +2483,40 @@ class depgraph(object):
 				self._dynamic_config._visible_pkgs[pkg.root].cpv_inject(pkg)
 		return ret
 
+	def _want_installed_pkg(self, pkg):
+		"""
+		Given an installed package returned from select_pkg, return
+		True if the user has not explicitly requested for this package
+		to be replaced (typically via an atom on the command line).
+		"""
+		if "selective" not in self._dynamic_config.myparams and \
+			pkg.root == self._frozen_config.target_root:
+			try:
+				next(self._iter_atoms_for_pkg(pkg))
+			except StopIteration:
+				pass
+			except portage.exception.InvalidDependString:
+				pass
+			else:
+				return False
+		return True
+
 	def _select_pkg_highest_available_imp(self, root, atom, onlydeps=False):
 		pkg, existing = self._wrapped_select_pkg_highest_available_imp(root, atom, onlydeps=onlydeps)
 
-		if pkg is None:
-			pkg, existing = self._wrapped_select_pkg_highest_available_imp(root, atom, \
-				onlydeps=onlydeps, allow_missing_keywords=True)
-			
-			if pkg is not None and not pkg.visible:
-				self._dynamic_config._needed_user_config_changes.setdefault(pkg, set()).add("unstable keyword")
+		if self._frozen_config.myopts.get('--autounmask', 'n') is True:
+			if pkg is not None and \
+				pkg.installed and \
+				not self._want_installed_pkg(pkg):
+				pkg = None
+			if pkg is None:
+				pkg, existing = \
+					self._wrapped_select_pkg_highest_available_imp(
+						root, atom, onlydeps=onlydeps,
+						allow_missing_keywords=True)
+
+				if pkg is not None and not pkg.visible:
+					self._dynamic_config._needed_user_config_changes.setdefault(pkg, set()).add("unstable keyword")
 
 		return pkg, existing
 
diff --git a/pym/_emerge/help.py b/pym/_emerge/help.py
index 43e9794ed..72bb56d41 100644
--- a/pym/_emerge/help.py
+++ b/pym/_emerge/help.py
@@ -291,6 +291,17 @@ def help(myopts, havecolor=1):
 			"EMERGE_DEFAULT_OPTS variable."
 		for line in wrap(desc, desc_width):
 			print(desc_indent + line)
+		print() 
+		print("       " + green("--autounmask") + "[=%s]" % turquoise("n"))
+		desc = "Automatically unmask packages. If any configuration " + \
+			"changes are required, then they will be displayed " + \
+			"after the merge list and emerge will immediately " + \
+			"abort. If the displayed configuration changes are " + \
+			"satisfactory, you should copy and paste them into " + \
+			"the specified configuration file(s). Currently, " + \
+			"this only works for unstable KEYWORDS masks."
+		for line in wrap(desc, desc_width):
+			print(desc_indent + line)
 		print()
 		print("       " + green("--backtrack") + " " + turquoise("COUNT"))
 		desc = "Specifies an integer number of times to backtrack if " + \
diff --git a/pym/_emerge/main.py b/pym/_emerge/main.py
index b2bb362f8..92df3bfb4 100644
--- a/pym/_emerge/main.py
+++ b/pym/_emerge/main.py
@@ -388,6 +388,7 @@ def insert_optional_args(args):
 	new_args = []
 
 	default_arg_opts = {
+		'--autounmask'           : ('n',),
 		'--complete-graph' : ('n',),
 		'--deep'       : valid_integers,
 		'--depclean-lib-check'   : ('n',),
@@ -515,6 +516,13 @@ def parse_opts(tmpcmdline, silent=False):
 
 	longopt_aliases = {"--cols":"--columns", "--skip-first":"--skipfirst"}
 	argument_options = {
+
+		"--autounmask": {
+			"help"    : "automatically unmask packages",
+			"type"    : "choice",
+			"choices" : ("True", "n")
+		},
+
 		"--accept-properties": {
 			"help":"temporarily override ACCEPT_PROPERTIES",
 			"action":"store"
@@ -735,6 +743,9 @@ def parse_opts(tmpcmdline, silent=False):
 
 	myoptions, myargs = parser.parse_args(args=tmpcmdline)
 
+	if myoptions.autounmask in ("True",):
+		myoptions.autounmask = True
+
 	if myoptions.changed_use is not False:
 		myoptions.reinstall = "changed-use"
 		myoptions.changed_use = False