phases: move root phase assignment to it's own function
This moves the initial root phase assignment to it's own function. Future
patches which make phase calculations lazy will use this function to pre-fill
certain phases which can be deduced from the roots.
#require serve
$ hg init server
$ cd server
$ cat >> .hg/hgrc << EOF
> [extensions]
> strip=
> EOF
$ echo 1 > foo
$ hg commit -A -m 'first'
adding foo
$ echo 2 > bar
$ hg commit -A -m 'second'
adding bar
Produce a bundle to use
$ hg strip -r 1
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
saved backup bundle to $TESTTMP/server/.hg/strip-backup/ed602e697e0f-backup.hg (glob)
Serve from a bundle file
$ hg serve -R .hg/strip-backup/ed602e697e0f-backup.hg -d -p $HGPORT --pid-file=hg.pid
$ cat hg.pid >> $DAEMON_PIDS
Ensure we're serving from the bundle
$ ("$TESTDIR/get-with-headers.py" localhost:$HGPORT 'file/tip/?style=raw')
200 Script output follows
-rw-r--r-- 2 bar
-rw-r--r-- 2 foo