revlog: simplify rawtext return value
We're always returning a tuple even though only the raw text is being used,
and we're rebuilding another tuple again higher.
As a bonus, this will remove one tuple creation and deletion
per `raw_text` call, hence fewer gc calls, etc.
$ hg init repo
$ cd repo
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls -A
.hg
a
unknown