Diff for "CaseFoldingPlan"

To deal with CaseFolding on the repo side, we need to:

• escape uppercase ASCII characters in filenames
• escape high ASCII
  • Unicode and other characters may be case-folded as well
  • Filesystems and operating systems may do other unfortunate things to
    • filenames which will cause interoperability trouble
• use the same scheme by default on all systems to avoid backup and media sharing issues

A simple escaping scheme is as follows:

• replace _ with __

• replace A-Z with _a, etc.
• replace characters 126-255 with ~7e to ~ff (note this escapes tilde as well

Note that we rarely need to

Implementation plan:

• add separate localrepo access methods for all store data (changelog, manifest, data/*, journal, lock)

• if .hg/data exists at localrepo init time, use old access scheme

• if not, access all store data with escaped paths inside .hg/store/ (eg .hg/store/00changelog.i or .hg/store/data/_readme.i)

This scheme will automatically escape all paths on newly cloned or created repos.

On the working directory side, the best we can do is detect collisions. A simple scheme might look something like this:

• detect case sensitive filesystem at checkout/update time
• scan manifest for case-folding collisions and issue a warning