revset: use decorator to mark a predicate as safe
Using decorator can localize changes for adding (or removing) a "safe"
revset predicate function in source code.
To avoid accidentaly treating unsuitable predicates as safe, this
patch uses False as default value of "safe" argument. This forces safe
predicates to be decorated with explicit 'safe=True'.
$ rm -rf a
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ hg tag t1 # 1
$ hg tag --remove t1 # 2
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg tag -f -r0 t1
$ hg tags
tip 3:a49829c4fc11
t1 0:f7b1eb17ad24
$ cd ..