tests/test-revlog-ancestry.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, print_function
import os
from mercurial import (
    hg,
    merge,
    ui as uimod,
)

u = uimod.ui.load()

repo = hg.repository(u, 'test1', create=1)
os.chdir('test1')

def commit(text, time):
    repo.commit(text=text, date="%d 0" % time)

def addcommit(name, time):
    f = open(name, 'w')
    f.write('%s\n' % name)
    f.close()
    repo[None].add([name])
    commit(name, time)

def update(rev):
    merge.update(repo, rev, False, True)

def merge_(rev):
    merge.update(repo, rev, True, False)

if __name__ == '__main__':
    addcommit("A", 0)
    addcommit("B", 1)

    update(0)
    addcommit("C", 2)

    merge_(1)
    commit("D", 3)

    update(2)
    addcommit("E", 4)
    addcommit("F", 5)

    update(3)
    addcommit("G", 6)

    merge_(5)
    commit("H", 7)

    update(5)
    addcommit("I", 8)

    # Ancestors
    print('Ancestors of 5')
    for r in repo.changelog.ancestors([5]):
        print(r, end=' ')

    print('\nAncestors of 6 and 5')
    for r in repo.changelog.ancestors([6, 5]):
        print(r, end=' ')

    print('\nAncestors of 5 and 4')
    for r in repo.changelog.ancestors([5, 4]):
        print(r, end=' ')

    print('\nAncestors of 7, stop at 6')
    for r in repo.changelog.ancestors([7], 6):
        print(r, end=' ')

    print('\nAncestors of 7, including revs')
    for r in repo.changelog.ancestors([7], inclusive=True):
        print(r, end=' ')

    print('\nAncestors of 7, 5 and 3, including revs')
    for r in repo.changelog.ancestors([7, 5, 3], inclusive=True):
        print(r, end=' ')

    # Descendants
    print('\n\nDescendants of 5')
    for r in repo.changelog.descendants([5]):
        print(r, end=' ')

    print('\nDescendants of 5 and 3')
    for r in repo.changelog.descendants([5, 3]):
        print(r, end=' ')

    print('\nDescendants of 5 and 4')
    print(*repo.changelog.descendants([5, 4]), sep=' ')