Add special "hook" mode to polint to fix language detection.

The language is detected from the filename which doesn't work when
called from the hook where a temporary file is processed.

src/hooks/pre-commit.hook

@@ -78,7 +78,7 @@ fi
 for file in `git diff-index --cached --name-only HEAD --diff-filter=ACMR| grep "\.po$"` ; do
     echo "Checking ${file}"
     nf=`git checkout-index --temp ${file} | cut -f 1`
-    ./src/i18n/helpers/polint.py "${nf}"
+    ./src/i18n/helpers/polint.py --hook "${nf}" "${file}"
     r=$?
     rm "${nf}"
     if [ $r != 0 ] ; then

src/i18n/helpers/polint.py

@@ -187,12 +187,27 @@ def main():
     _, POT_DATA, _ = parsepo(os.path.join(ROOT, 'messages.pot'))
 
     errors = 0
+    try:
+        sys.argv.remove('--hook')
+    except ValueError:
+        is_hook = False
+    else:
+        is_hook = True
+
+    if is_hook:
+        filename, orig_filename = sys.argv[1:]
+        filenames = [filename]
+    else:
+        orig_filename = None
         filenames = sys.argv[1:]
     show_filenames = False
     if not filenames:
         filenames = glob.glob(os.path.join(ROOT, 'messages-*.po'))
         show_filenames = True
     for filename in filenames:
+        if orig_filename:
+            language = os.path.basename(orig_filename)[9:-3]
+        else:
             language = os.path.basename(filename)[9:-3]
         if show_filenames:
             print 'Checking %s (%s)' % (filename, language)