diff -r 000000000000 -r 6474c204b198 python/mozbuild/mozpack/unify.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/python/mozbuild/mozpack/unify.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,192 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mozpack.files import (
+    BaseFinder,
+    JarFinder,
+    ExecutableFile,
+    BaseFile,
+    GeneratedFile,
+)
+from mozpack.executables import (
+    MACHO_SIGNATURES,
+)
+from mozpack.mozjar import JarReader
+from mozpack.errors import errors
+from tempfile import mkstemp
+import mozpack.path
+import struct
+import os
+import subprocess
+from collections import OrderedDict
+
+
+def may_unify_binary(file):
+    '''
+    Return whether the given BaseFile instance is an ExecutableFile that
+    may be unified. Only non-fat Mach-O binaries are to be unified.
+    '''
+    if isinstance(file, ExecutableFile):
+        signature = file.open().read(4)
+        if len(signature) < 4:
+            return False
+        signature = struct.unpack('>L', signature)[0]
+        if signature in MACHO_SIGNATURES:
+            return True
+    return False
+
+
+class UnifiedExecutableFile(BaseFile):
+    '''
+    File class for executable and library files that to be unified with 'lipo'.
+    '''
+    def __init__(self, executable1, executable2):
+        '''
+        Initialize a UnifiedExecutableFile with a pair of ExecutableFiles to
+        be unified. They are expected to be non-fat Mach-O executables.
+        '''
+        assert isinstance(executable1, ExecutableFile)
+        assert isinstance(executable2, ExecutableFile)
+        self._executables = (executable1, executable2)
+
+    def copy(self, dest, skip_if_older=True):
+        '''
+        Create a fat executable from the two Mach-O executable given when
+        creating the instance.
+        skip_if_older is ignored.
+        '''
+        assert isinstance(dest, basestring)
+        tmpfiles = []
+        try:
+            for e in self._executables:
+                fd, f = mkstemp()
+                os.close(fd)
+                tmpfiles.append(f)
+                e.copy(f, skip_if_older=False)
+            subprocess.call(['lipo', '-create'] + tmpfiles + ['-output', dest])
+        finally:
+            for f in tmpfiles:
+                os.unlink(f)
+
+
+class UnifiedFinder(BaseFinder):
+    '''
+    Helper to get unified BaseFile instances from two distinct trees on the
+    file system.
+    '''
+    def __init__(self, finder1, finder2, sorted=[], **kargs):
+        '''
+        Initialize a UnifiedFinder. finder1 and finder2 are BaseFinder
+        instances from which files are picked. UnifiedFinder.find() will act as
+        FileFinder.find() but will error out when matches can only be found in
+        one of the two trees and not the other. It will also error out if
+        matches can be found on both ends but their contents are not identical.
+
+        The sorted argument gives a list of mozpack.path.match patterns. File
+        paths matching one of these patterns will have their contents compared
+        with their lines sorted.
+        '''
+        assert isinstance(finder1, BaseFinder)
+        assert isinstance(finder2, BaseFinder)
+        self._finder1 = finder1
+        self._finder2 = finder2
+        self._sorted = sorted
+        BaseFinder.__init__(self, finder1.base, **kargs)
+
+    def _find(self, path):
+        '''
+        UnifiedFinder.find() implementation.
+        '''
+        files1 = OrderedDict()
+        for p, f in self._finder1.find(path):
+            files1[p] = f
+        files2 = set()
+        for p, f in self._finder2.find(path):
+            files2.add(p)
+            if p in files1:
+                if may_unify_binary(files1[p]) and \
+                        may_unify_binary(f):
+                    yield p, UnifiedExecutableFile(files1[p], f)
+                else:
+                    err = errors.count
+                    unified = self.unify_file(p, files1[p], f)
+                    if unified:
+                        yield p, unified
+                    elif err == errors.count:
+                        self._report_difference(p, files1[p], f)
+            else:
+                errors.error('File missing in %s: %s' %
+                             (self._finder1.base, p))
+        for p in [p for p in files1 if not p in files2]:
+            errors.error('File missing in %s: %s' % (self._finder2.base, p))
+
+    def _report_difference(self, path, file1, file2):
+        '''
+        Report differences between files in both trees.
+        '''
+        errors.error("Can't unify %s: file differs between %s and %s" %
+                     (path, self._finder1.base, self._finder2.base))
+        if not isinstance(file1, ExecutableFile) and \
+                not isinstance(file2, ExecutableFile):
+            from difflib import unified_diff
+            for line in unified_diff(file1.open().readlines(),
+                                     file2.open().readlines(),
+                                     os.path.join(self._finder1.base, path),
+                                     os.path.join(self._finder2.base, path)):
+                errors.out.write(line)
+
+    def unify_file(self, path, file1, file2):
+        '''
+        Given two BaseFiles and the path they were found at, check whether
+        their content match and return the first BaseFile if they do.
+        '''
+        content1 = file1.open().readlines()
+        content2 = file2.open().readlines()
+        if content1 == content2:
+            return file1
+        for pattern in self._sorted:
+            if mozpack.path.match(path, pattern):
+                if sorted(content1) == sorted(content2):
+                    return file1
+                break
+        return None
+
+
+class UnifiedBuildFinder(UnifiedFinder):
+    '''
+    Specialized UnifiedFinder for Mozilla applications packaging. It allows
+    "*.manifest" files to differ in their order, and unifies "buildconfig.html"
+    files by merging their content.
+    '''
+    def __init__(self, finder1, finder2, **kargs):
+        UnifiedFinder.__init__(self, finder1, finder2,
+                               sorted=['**/*.manifest'], **kargs)
+
+    def unify_file(self, path, file1, file2):
+        '''
+        Unify buildconfig.html contents, or defer to UnifiedFinder.unify_file.
+        '''
+        if mozpack.path.basename(path) == 'buildconfig.html':
+            content1 = file1.open().readlines()
+            content2 = file2.open().readlines()
+            # Copy everything from the first file up to the end of its <body>,
+            # insert a <hr> between the two files and copy the second file's
+            # content beginning after its leading <h1>.
+            return GeneratedFile(''.join(
+                content1[:content1.index('</body>\n')] +
+                ['<hr> </hr>\n'] +
+                content2[content2.index('<h1>about:buildconfig</h1>\n') + 1:]
+            ))
+        if path.endswith('.xpi'):
+            finder1 = JarFinder(os.path.join(self._finder1.base, path),
+                                JarReader(fileobj=file1.open()))
+            finder2 = JarFinder(os.path.join(self._finder2.base, path),
+                                JarReader(fileobj=file2.open()))
+            unifier = UnifiedFinder(finder1, finder2, sorted=self._sorted)
+            err = errors.count
+            all(unifier.find(''))
+            if err == errors.count:
+                return file1
+            return None
+        return UnifiedFinder.unify_file(self, path, file1, file2)