remove `export_hashes` from Patch objects, not used anymore since 9609c2c2574e8bb36764ff0ffe61c51f67c7c323
allow no-op patches to be deleted even if they have children
make the Commit Workspace button disabled if there is nothing to commit
implement @konklone's idea of asking for a name before creating a patch so that we can perform some validation to encourage good patch names
tabbify edit file/new file