An automatic versioning fuse filesystem
Erst is a fuse filesystem that does automatic versioning. It uses a mercurial repository to do the revision control.
It runs single threaded because it uses mercurial update command to switch the “view” you have of the filesystem. In most cases this won’t be much of a penalty, but if you have multiple things accessing the filesystem using different time views, it could impact performance.
Past file access is read only. To access a past version of the file simply put an iso 8601 timestamp as the leading element of the path, after the path to the mountpoint.
For example if your filesystem is mounted as /tmp/project_n, you could access what it looked like on Jan6, 2014 by doing /tmp/project_n/2014-01-06. With just a date it gives you the “end of the day” view. You can also include a specific timestamp to further control when, /tmp/project_n/2014-01-06T13:30:20
Timestamps are in 24 hour clock style, by default it’s considered local time, if you’d like it to be UTC instead, add a Z to the end, /tmp/project_n/2014-01-06T13:30:20Z
Things get commited on the close, create, and remove operations.
Renaming ends up being tricky, it doesn’t use hg rename, so some of the history is lost if you examine the repository.
I don’t recommend using this to store large binary files, it’ll work, but it can make the repository a lost slower when switching between views.
Files added to the “repo” directory outside of mercurial or erst won’t be seen by erst. Erst uses the mercurial manifest to determine what files should appear in a given view.
- Erst ignores files with specific endings:
- currently .swp, .swpx, .swo, .swn, .o, ~, .hg
It does this to avoid temporary swap files made by emacs, vi(m), and compiling. If you want to change this on your system, just modify the __ignore list in the Erst class. Maybe one day there will be a config file that will contain that, instead of having to modify the source.
You can also use Erst to “mount” an existing mercurial repo that was not created by Erst.