bookmarks: update help text since moving into core
Clarifies the help text for the bookmarks command regarding the
requirements for pushing or pulling bookmarks.
test that 'hg commit' does not crash if the user removes a newly added file
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ touch b
$ hg add b
$ rm b
$ hg commit -A -m"comment #1"
removing b
nothing changed
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