Problem: on large repos, it would be useful to be able to do a partial clone and/or checkout
Proposal: add a new file like .hgignore to the .hg/ directory that specifies which files should be ignored for clone/checkout.
[http://www.selenic.com/mercurial/bts/issue105 Issue105 in the BTS] covers partial checkouts and suggests using -X/-I on clone or checkout.
To implement:
- pick a sensible name for this file (BryanOSullivan suggests ignoremissing)
- teach localrepo to use this filtering where appropriate (checkout, pull)
- teach changegroup to choke if someone attempts to pull a changeset from us with a file we don't have
Not to be confused with TrimmingHistory, which trims in the history tree, not the directory tree.
Comments from Matt Mackall:
> > How hard would this be to implement?
On a scale of 1 to 10, I'd rate it about a 7.
The simplest approach is probably "allow cloning of subdirectories". Here's how that would work:
- add a file called "subdir" to .hg/store containing the subdirectory we're cloning
- do a clone as usual, but don't write out revlogs that aren't in subdir
- adjust the functions dealing with paths (localrepo.wjoin, etc.) appropriately
- teach various things (checkout, status, etc.) to skip files outside the subdirectory
- teach merge not allow merging when files outside the subdirectory conflict
Merging is the tricky part, and I expect there's a gotcha or two buried in there.