Update to r25.
Changelog:
- A new dironly option is added to only show directories and hide regular files
- A new dircache option is added to disable caching of directories
- Two new commands filter and setfilter is added along with a new option incfilter and a promptfmt expansion %F to implement directory filtering feature
- A new special command pre-cd is added to run a command before a directory is changed
- cmap command now accepts all expressions similar to map
- Marking a symlink directory should now save the symlink path instead of the target path
- A number of crashes have been fixed when hidden option is changed