Teach walk code about absolute paths. The first consequence of this is that absolute and relative paths now all work in the same way. The second is that paths that lie outside the repository now cause an error to be reported, instead of something arbitrary and expensive being done. Internally, all of the serious work is in the util package. The new canonpath function takes an arbitrary path and either returns a canonical path or raises an error. Because it needs to know where the repository root is, it must be fed a repository or dirstate object, which has given commands.matchpats and friends a new parameter to pass along. The util.matcher function uses this to canonicalise globs and relative path names. Meanwhile, I've moved the Abort exception from commands to util, and killed off the redundant util.CommandError exception.

+ hg init
+ hg add t1
+ hg commit -m 1 -d 0 0
+ hg clone a b
+ hg add t2
+ hg commit -m 2 -d 0 0
+ hg add t3
+ hg commit -m 3 -d 0 0
+ hg push ../a
pushing to ../a
searching for changes
abort: unsynced remote changes!
(did you forget to sync? use push -f to force)
+ hg pull ../a
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
+ hg push ../a
pushing to ../a
searching for changes
abort: push creates new remote branches!
(did you forget to merge? use push -f to force)
+ hg up -m
+ hg commit -m 4 -d 0 0
+ hg push ../a
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files