$ hg init a
$ cd a
$ echo a > a
$ hg add -n
adding a
$ hg st
? a
$ hg add
adding a
$ hg st
A a
$ hg forget a
$ hg add
adding a
$ hg st
A a
$ echo b > b
$ hg add -n b
$ hg st
A a
? b
$ hg add b || echo "failed to add b"
$ hg st
A a
A b
should fail
$ hg add b
b already tracked!
$ hg st
A a
A b
$ hg ci -m 0 --traceback
should fail
$ hg add a
a already tracked!
$ echo aa > a
$ hg ci -m 1
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo aaa > a
$ hg ci -m 2
created new head
$ hg merge
merging a
warning: conflicts during merge.
merging a failed!
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges or 'hg update -C' to abandon
$ hg st
M a
? a.orig
should fail
$ hg add a
a already tracked!
$ hg st
M a
? a.orig
$ hg resolve -m a
$ hg ci -m merge
issue683
$ hg forget a
$ hg add a
$ hg st
? a.orig
$ hg rm a
$ hg st
R a
? a.orig
$ echo a > a
$ hg add a
$ hg st
M a
? a.orig
$ hg add c && echo "unexpected addition of missing file"
c: No such file or directory
$ echo c > c
$ hg add d c && echo "unexpected addition of missing file"
d: No such file or directory
$ hg st
M a
A c
? a.orig