diff: Support .gitattribute encodings when applying diffs

Teach the diff editor to apply diffs for files with non-utf-8 encodings.
We now write patch files according to the encoding specified using
.gitattributes.

Closes #96

Reported-by: @mmark on github.com
Helped-by: Ingo Weinhold <ingo_weinhold@gmx.de>
Signed-off-by: David Aguilar <davvid@gmail.com>

cola/core.py

@@ -35,10 +35,12 @@ def decode(enc, encoding=None):
     return unicode(enc)
 
 
-def encode(unenc):
+def encode(unenc, encoding=None):
     """encode(unencoded_string) returns a string encoded in utf-8
     """
-    return unenc.encode('utf-8', 'replace')
+    if encoding is None:
+        encoding = 'utf-8'
+    return unenc.encode(encoding, 'replace')
 
 
 @interruptable

cola/diffparse.py

@@ -3,6 +3,7 @@
 
 from cola import utils
 from cola import gitcmds
+from cola import gitcfg
 
 
 class DiffParser(object):
@@ -18,13 +19,15 @@ def __init__(self, model, filename='',
         self._diff_spans = []
         self._diff_offsets = []
 
+        self.config = gitcfg.instance()
         self.head = model.head
         self.amending = model.amending()
         self.start = None
         self.end = None
         self.offset = None
         self.diffs = []
         self.selected = []
+        self.filename = filename
 
         (header, diff) = gitcmds.diff_helper(head=self.head,
                                              amending=self.amending,
@@ -49,7 +52,9 @@ def write_diff(self,filename,which,selected=False,noop=False):
         """Writes a new diff corresponding to the user's selection."""
         if not noop and which < len(self.diffs):
             diff = self.diffs[which]
-            utils.write(filename, self.header + '\n' + diff + '\n')
+            encoding = self.config.file_encoding(self.filename)
+            utils.write(filename, self.header + '\n' + diff + '\n',
+                        encoding=encoding)
             return True
         else:
             return False
@@ -221,12 +226,13 @@ def process_diff_selection(self, selected, offset, selection,
         status = 0
         # Process diff selection only
         if selected:
+            encoding = self.config.file_encoding(self.filename)
             for idx in self.selected:
                 contents = self.diff_subset(idx, start, end)
                 if not contents:
                     continue
                 tmpfile = utils.tmp_filename('selection')
-                utils.write(tmpfile, contents)
+                utils.write(tmpfile, contents, encoding=encoding)
                 if apply_to_worktree:
                     stat, out = self.model.apply_diff_to_worktree(tmpfile)
                     output += out

cola/utils.py

@@ -237,10 +237,10 @@ def slurp(path):
     return core.decode(slushy)
 
 
-def write(path, contents):
+def write(path, contents, encoding=None):
     """Writes a raw string to a file."""
     fh = open(core.encode(path), 'wb')
-    core.write(fh, core.encode(contents))
+    core.write(fh, core.encode(contents, encoding=encoding))
     fh.close()