purge: abort with missing files avoiding problems with name-mangling fs
In a name mangling filesystem (e.g. a case insensitive one)
dirstate.walk() can yield filenames different from the ones
stored in the dirstate. This already confuses the status and
add commands, but with purge this may cause data loss.
To prevent this purge refuses to work if there are missing
files and has a 'force' option if the user knows it is safe.
Even with the force option purge checks if any of the missing
files is still available in the working dir: if so there
may be some problem with the underlying filesystem, so it
unconditionally aborts.
% init foo-base
% create alpha in first repo
adding alpha
% clone foo-base to foo-work
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% create beta in second repo
adding beta
% create gamma in first repo
adding gamma
% pull into work and merge
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
% revert to changeset 1 to simulate a failed merge
2 files updated, 0 files merged, 0 files removed, 0 files unresolved