purge: fix b777dd8f7836 (remove read-only files)

- use try/except to avoid unnecessary work
- edit only mode bits

hgext/purge.py

@@ -73,10 +73,14 b' def purge(ui, repo, *dirs, **opts):'
             ui.write('%s%s' % (name, eol))
 
     def removefile(path):
+        try:
+            os.remove(path)
+        except OSError:
         # read-only files cannot be unlinked under Windows
         s = os.stat(path)
-        if (s.st_dev & stat.S_IWRITE) == 0:
-            os.chmod(path, s.st_mode | stat.S_IWRITE)
+            if (s.st_mode & stat.S_IWRITE) != 0:
+                raise
+            os.chmod(path, stat.S_IMODE(s.st_mode) | stat.S_IWRITE)
         os.remove(path)
 
     directories = []

tests/test-purge

@@ -38,7 +38,7 b' touch untracked_file_readonly'
 python <<EOF
 import os, stat
 f= 'untracked_file_readonly'
-os.chmod(f, os.stat(f).st_mode & ~stat.S_IWRITE)
+os.chmod(f, stat.S_IMODE(os.stat(f).st_mode) & ~stat.S_IWRITE)
 EOF
 hg purge -p
 hg purge -v