tests/test-empty-group

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.

#!/bin/sh
#
#  A          B    
#  
#  3  4       3    
#  |\/|       |\   
#  |/\|       | \  
#  1  2       1  2 
#  \ /        \ /  
#   0          0
#
# if the result of the merge of 1 and 2
# is the same in 3 and 4, no new manifest
# will be created and the manifest group
# will be empty during the pull
#
# (plus we test a failure where outgoing
# wrongly reported the number of csets)
#

hg init a
cd a
touch init
hg ci -A -m 0 -d "1000000 0"
touch x y
hg ci -A -m 1 -d "1000000 0"
hg update 0
touch x y
hg ci -A -m 2 -d "1000000 0"
hg merge 1
hg ci -A -m m1 -d "1000000 0"
#hg log
#hg debugindex .hg/store/00manifest.i
hg update -C 1
hg merge 2
hg ci -A -m m2 -d "1000000 0"
#hg log
#hg debugindex .hg/store/00manifest.i

cd ..
hg clone -r 3 a b
hg clone -r 4 a c
hg -R a outgoing b
hg -R a outgoing c
hg -R b outgoing c
hg -R c outgoing b

hg -R b pull a
hg -R c pull a