largefiles: fix a traceback in lfconvert if a largefile is missing (
issue3519)
The largefile may be missing for various reasons, including that a remote
repository was cloned without the --all-largefiles option. Therefore, it seems
reasonable to attempt to download the missing files and failing that, abort and
indicate the affected file and revision so the user can manually fix the
problem.
basic test for hg debugrebuildstate
$ hg init repo
$ cd repo
$ touch foo bar
$ hg ci -Am 'add foo bar'
adding bar
adding foo
$ touch baz
$ hg add baz
$ hg rm bar
$ hg debugrebuildstate
state dump after
$ hg debugstate --nodates | sort
n 644 -1 bar
n 644 -1 foo
status
$ hg st -A
! bar
? baz
C foo
$ cd ..