tests/test-dispatch.py.out

scmutil: improve documentation of revset APIs

I can never remember the differences between the various revset
APIs. I can never remember that scmutil.revrange() is the one I
want to use from user-facing commands.

Add some documentation to clarify this.

While we're here, the argument name for revrange() is changed to
"specs" because that's what it actually is.

running: init test1
result: None
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: None
running: commit -m commit2 -d 2000-01-02 foo
result: None
running: log -r 0
changeset:   0:0e4634943879
user:        test
date:        Sat Jan 01 00:00:00 2000 +0000
summary:     commit1

result: None
running: log -r tip
changeset:   1:45589e459b2e
tag:         tip
user:        test
date:        Sun Jan 02 00:00:00 2000 +0000
summary:     commit2

result: None