Repair new with patchdescr.template (#87)

When a user-provided patchdescr.tmpl is present, `stg new` would crash
with a TypeError due to a str/bytes mismatch.

Repairs #87.

Signed-off-by: Peter Grayson <pete@jpgrayson.net>

stgit/commands/common.py

@@ -466,7 +466,7 @@ def update_commit_data(cd, message=None, author=None, sign_str=None, edit=False)
     if edit:
         tmpl = templates.get_template('patchdescr.tmpl')
         if tmpl:
-            cd = cd.set_message(cd.message + tmpl)
+            cd = cd.set_message(cd.message_str + tmpl)
         cd = cd.set_message(edit_bytes(cd.message, '.stgit-new.txt'))
 
     return cd

t/t1003-new.sh

@@ -80,6 +80,13 @@ test_expect_success \
     test_path_is_file new-tmpl.txt
 '
 
+test_expect_success \
+    'New with patchdescr.tmpl' '
+    echo "Patch Description Template" > .git/patchdescr.tmpl &&
+    stg new templated-patch &&
+    stg show | grep "Patch Description Template"
+'
+
 test_expect_failure \
     'Patch with slash in name' '
     stg new bar/foo -m "patch bar/foo"