py3: manually import pycompat.open into files that need it
We want to eliminate the source transformer. Currently it inserts
a `from mercurial.pycompat import ...` at the top of files to alias
some builtins.
This commit replaces the implicit import of `open` with an explicit
import on files that need it and changes the source transformer to
no longer import `open`.
As part of this, we needed to store an explicit local for `open` in
the Python 2 code path in `pycompat` so the import works. (Builtins
that are automatically in scope cannot be imported.)
Differential Revision: https://phab.mercurial-scm.org/D7005
#require no-windows
$ . "$TESTDIR/remotefilelog-library.sh"
$ hg init master
$ cd master
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> server=True
> serverexpiration=-1
> EOF
$ echo x > x
$ hg commit -qAm x
$ echo y > y
$ hg commit -qAm y
$ echo z > z
$ hg commit -qAm z
$ cd ..
$ hgcloneshallow ssh://user@dummy/master shallow -q
3 files fetched over 1 fetches - (3 misses, 0.00% hit ratio) over *s (glob)
# Compute keepset for 0th and 2nd commit, which implies that we do not process
# the 1st commit, therefore we diff 2nd manifest with the 0th manifest and
# populate the keepkeys from the diff
$ cd shallow
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> pullprefetch=0+2
> EOF
$ hg debugkeepset
# Compute keepset for all commits, which implies that we only process deltas of
# manifests of commits 1 and 2 and therefore populate the keepkeys from deltas
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> pullprefetch=all()
> EOF
$ hg debugkeepset