tests/test-symlink-os-yes-fs-no.py

repair: move check for existing transaction earlier

Several benefits:

 * Gets close the comment describing it
 * Splits off unrelated comment about "backup" argument
 * Error checking is customarily done early
 * If we added an early return to the method, it would still
   consistently fail if there was an existing transaction (so
   we would find and fix that case quickly)

One test needs updating with for this change, because we no longer
create the backup bundle before we fail. I don't see much reason to
create that backup bundle. If some command was adding content and then
trying to strip it as well within the transaction, we would have a
backup for the user, but the risk of that not being discovered in
development seems very small.

from __future__ import absolute_import

import os
import sys
import time
from mercurial import (
    commands,
    hg,
    ui as uimod,
    util,
)

TESTDIR = os.environ["TESTDIR"]
BUNDLEPATH = os.path.join(TESTDIR, 'bundles', 'test-no-symlinks.hg')

# only makes sense to test on os which supports symlinks
if not getattr(os, "symlink", False):
    sys.exit(80) # SKIPPED_STATUS defined in run-tests.py

u = uimod.ui.load()
# hide outer repo
hg.peer(u, {}, '.', create=True)

# clone with symlink support
hg.clone(u, {}, BUNDLEPATH, 'test0')

repo = hg.repository(u, 'test0')

# wait a bit, or the status call wont update the dirstate
time.sleep(1)
commands.status(u, repo)

# now disable symlink support -- this is what os.symlink would do on a
# non-symlink file system
def symlink_failure(src, dst):
    raise OSError(1, "Operation not permitted")
os.symlink = symlink_failure
def islink_failure(path):
    return False
os.path.islink = islink_failure

# dereference links as if a Samba server has exported this to a
# Windows client
for f in 'test0/a.lnk', 'test0/d/b.lnk':
    os.unlink(f)
    fp = open(f, 'wb')
    fp.write(util.readfile(f[:-4]))
    fp.close()

# reload repository
u = uimod.ui.load()
repo = hg.repository(u, 'test0')
commands.status(u, repo)

# try cloning a repo which contains symlinks
u = uimod.ui.load()
hg.clone(u, {}, BUNDLEPATH, 'test1')